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Vitamin D deficiency in northern Taiwan: A community-based cohort study

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Background Vitamin D deficiency has become an important public health problem, however few studies have been conducted in subtropical countries, and the predictors of vitamin D deficiency in people with healthy renal function are unclear. The objective of this study was to evaluate the prevalence and factors associated with vitamin D deficiency in northern Taiwan. Methods The cross-sectional study was performed between August 2013 and August 2017, and included 3954 participants without chronic kidney disease (CKD) aged ≥30 years in northern Taiwan. Serum 25-hydroxyvitamin D [25(OH)-D] levels, biochemistry, sociodemographic variables (age, sex, education, occupation) and lifestyle habits (tea, coffee consumption and physical activities) were recorded. Associations between vitamin D status and these variables were examined using a regression model. The definition of deficiency was defined as a serum 25(OH)-D level < 20 ng/mL (50 nmol/L). Results The mean 25(OH)-D concentration was 28.9 ng/mL, and 22.4% of the study population had vitamin D deficiency. There was a significantly higher vitamin D deficiency ratio in the women compared to the men (22.9% vs 9.9%, p < 0.001). Vitamin D deficiency was most prevalent (38.4%) in those aged 30–39 years. Those with a graduate degree had the highest rate of vitamin D deficiency (31.5%). The predictors of vitamin D deficiency included female sex, young age, high education level, living in an urban area and physical inactivity. Tea consumption was negatively associated with vitamin D deficiency. Conclusions Vitamin D deficiency is prevalent in subtropical areas such as northern Taiwan in healthy individuals without CKD.
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R E S E A R C H A R T I C L E Open Access
Vitamin D deficiency in northern Taiwan: a
community-based cohort study
Ming-Jse Lee
1
, Heng-Jung Hsu
1,2,3
, I-Wen Wu
1,2
, Chiao-Yin Sun
1,2
, Ming-Kuo Ting
4
and Chin-Chan Lee
1,2*
Abstract
Background: Vitamin D deficiency has become an important public health problem, however few studies have
been conducted in subtropical countries, and the predictors of vitamin D deficiency in people with healthy renal
function are unclear. The objective of this study was to evaluate the prevalence and factors associated with vitamin
D deficiency in northern Taiwan.
Methods: The cross-sectional study was performed between August 2013 and August 2017, and included 3954
participants without chronic kidney disease (CKD) aged 30 years in northern Taiwan. Serum 25-hydroxyvitamin D
[25(OH)-D] levels, biochemistry, sociodemographic variables (age, sex, education, occupation) and lifestyle habits
(tea, coffee consumption and physical activities) were recorded. Associations between vitamin D status and these
variables were examined using a regression model. The definition of deficiency was defined as a serum 25(OH)-D
level < 20 ng/mL (50 nmol/L).
Results: The mean 25(OH)-D concentration was 28.9 ng/mL, and 22.4% of the study population had vitamin D
deficiency. There was a significantly higher vitamin D deficiency ratio in the women compared to the men
(22.9% vs 9.9%, p< 0.001). Vitamin D deficiency was most prevalent (38.4%) in those aged 3039 years. Those with a
graduate degree had the highest rate of vitamin D deficiency (31.5%). The predictors of vitamin D deficiency
included female sex, young age, high education level, living in an urban area and physical inactivity. Tea
consumption was negatively associated with vitamin D deficiency.
Conclusions: Vitamin D deficiency is prevalent in subtropical areas such as northern Taiwan in healthy individuals
without CKD.
Keywords: Vitamin D deficiency, Prevalence, Risk factor, Taiwan
Background
The important role of vitamin D, a fat-soluble vitamin
responsible for calcium and phosphate resorption, in
bone health and mineralization is well known [1,2].
Vitamin D deficiency may cause secondary hyperpara-
thyroidism, rickets, osteomalacia, osteoporosis, and even
fragility fractures [3]. In the past decade, vitamin D has
also been shown to be involved in a wide variety of
extra-skeletal effects, and its deficiency has been associ-
ated with several health conditions including muscle
weakness [4], diabetes mellitus [5], chronic kidney
disease [6], cancer [7,8], cardiovascular disease [4], in-
fection, and autoimmune disease [9].
Vitamin D can be obtained from sun light or natural
food. However, natural food sources of vitamin D are
limited and mainly come from animal food in the form
of vitamin D3 only [10]. Thus, without artificial supple-
ments or vitamin-fortified food, the major source of
vitamin D comes from the action of ultraviolet-B light
upon the 7-dehydrocholesterol of the skin. Several
factors may influence the production of vitamin D in the
skin, including aging, latitude, skin pigmentation, season,
use of sun screen, outdoor activities and air pollution
[11,12].
Vitamin D deficiency has been reported to be more
common than previously thought, and it has become a
public health issue in modern societies [13,14]. Many
© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
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reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
* Correspondence: leefang@adm.cgmh.org.tw
1
Division of Nephrology, Chang Gung Memorial Hospital, 222 Mai-Chin Road,
Keelung 204, Taiwan
2
College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
Full list of author information is available at the end of the article
Lee et al. BMC Public Health (2019) 19:337
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population-based studies on vitamin D deficiency have
been conducted, however most have been performed in
temperate countries with few being conducted in sub-
tropical regions. Because the prevalence of vitamin D
deficiency varies significantly in different countries and
populations [15], investigating the prevalence and associ-
ated sociodemographic factors of vitamin D deficiency
in subtropical areas is needed. In addition, to the best of
our knowledge, no previous study has focused on
healthy individuals without chronic kidney disease
(CKD). Since the level of 25(OH)-D declines with renal
function [16,17], CKD may influence the results related
to 25(OH)-D deficiency. In the present study, we evalu-
ated the 25(OH)-D concentrations, lifestyle habits, exer-
cise habits and past medical history, and also several
demographic and laboratory variables from a large sam-
ple of individuals without CKD in Keelung, a northern
city in Taiwan (latitude 25 N0800), to examine the
prevalence and sociodemographic factors independently
associated with 25 (OH) vitamin D [25(OH)-D] levels.
Methods
Study population and design
The study is based on data of a community health activ-
ity in four districts (Wanli, Ruifang, Gongliao and Anle)
in northern Taiwan from August 2013 to August 2017.
The community health activity included routine health
examinations (including blood tests and urine analysis)
and a questionnaire on health behavior for all residents
in the community. The aim of this program was to
detect and treat any health problems early and promote
health. Residents of the four districts who aged 30 years
and were not pregnant could join the health activity vol-
untarily after obtaining written informed consent. A
total of 4925 participants joined the healthy activity and
represent 4.2% of the population ages 30 and above in
the four districts. All of the participants were enrolled.
After excluding 971 participants with CKD, we obtained
a cohort of 3954 participants. The participants were di-
vided into two groups according to the level of plasma
25(OH)D; those with a level < 20 ng/mL (50 nmol/L)
were considered to be vitamin D deficient [18,19].
Demographic data (age, sex, residential district, occupa-
tion, and education level) and lifestyle habits (tea, coffee
consumption and exercise) were assessed from the ques-
tionnaires. Anthropometric and biochemistry measure-
ments were performed at entry to the study. Blood
samples were obtained after an overnight fast, and the
following parameters were determined: complete blood
cell count, liver and renal biochemistry parameters, lipid
profiles, fasting sugar, insulin, homeostatic model assess-
ment of insulin resistance (HOMA IR), intact parathy-
roid hormone (iPTH) and total 25(OH)-D levels. This
study was approved by the Ethics Committee of the
Institutional Review Board of Keelung Chang Gung Me-
morial Hospital.
Laboratory studies and definitions
We obtained complete laboratory profiles for individuals
in both groups. The laboratory parameters included the
plasma levels of blood urea nitrogen (BUN), creatinine,
hemoglobin, albumin, high sensitive C reactive protein
(hs-CRP), calcium, phosphate, alkaline phosphate, iPTH,
hemoglobin A1C and cholesterol. Plasma levels of BUN,
creatinine, hemoglobin, albumin, hs-CRP, calcium, phos-
phate, and cholesterol were assessed by spectrophoto-
metric analysis using a modified kinetic Jaffe reaction
with standardization of the creatinine calibration to an
isotope dilution mass spectrometry reference measure-
ment procedure. Plasma iPTH levels were measured
using a commercially available radioimmunoassay kit
(Scantibodies Laboratory; Santee, CA, USA). Serum level
of 25(OH)-D was measured using an electro-chemilumi-
nescence immunoassay (Cobas® Vitamin D3 assay, Roche
Diagnostics GmbH, Mannheim, Germany) with an inter-
assay coefficient of variation of 2.213.6%.
Chronic kidney disease was defined according to the
National Kidney Foundation K/DOQI classification for
CKD as persistent proteinuria or a decreased estimated
glomerular filtration rate (eGFR) of < 60 mL/min/1.73
m
2
, determined using the abbreviated Modification of
Diet in Renal Disease equation [20]. Proteinuria was
defined as a urine albumin-to-creatinine ratio > 30 mg/g
or urine protein-to-creatinine ratio > 150 mg/g. Vitamin
D deficiency was defined as a 25(OH)-D level <20 ng/
mL (50 nmol/L). Body mass index (BMI) was calculated
as the weight in kilograms divided by the square of the
height in meters. The participants were defined as being
tea and coffee drinkers if they had regularly drunk tea
and coffee for > 5 years. The physical activity level was
determined by weighting the reported hours per day of
any physical activity such as walking, dancing, garden-
ing, hiking, and swimming.
Statistical methods
Demographic and anthropometric statistics were ex
pressed as mean ± standard deviation as appropriate.
The Students t-test was used to compare the means of
continuous variables. Categorical data were tested using
the Chi-square test. The prevalence of vitamin D defi-
ciency was determined by sex, age group, education
level, occupation, residential district, tea and coffee
intake. Multiple logistic regression analysis was used to
identify the independent predictors of vitamin D defi-
ciency. Variables with a Pvalue < 0.05 and tea consump-
tion, which has been mentioned to have association with
vitamin D deficiency, were included in the multiple
logistic regression analysis. All reported Pvalues were
Lee et al. BMC Public Health (2019) 19:337 Page 2 of 8
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two-tailed, and were considered to be statistically signifi-
cant if they were < 0.05. Data were analyzed using SPSS
17.0 for Windows (SPSS Inc., Chicago, IL).
Results
A total of 3954 individuals without CKD aged 30 years
were included in this study. The mean age of the study
population was 55.48 ± 12.64 years. The mean 25(OH)-D
concentration of the study group was 28.94 ± 10.27 ng/
mL. Overall, 22.4% of the study population had a
25(OH)-D concentration < 20 ng/mL, and were defined
as having vitamin D deficiency. Significantly more
women had vitamin D deficiency than men (22.9% vs
9.9%, P< 0.001). The characteristics of the study group
are presented in Table 1. The mean age of the normal
vitamin D group was older than that of the vitamin D
deficiency group (56.98 ± 12.18 vs 48.81 ± 12.53 years; P
< 0.001). There were significantly more men in the nor-
mal vitamin D group than in the vitamin D deficiency
group (38.8% vs 19.1; P< 0.001). In addition, the normal
vitamin D group had a lower iPTH level (43.50 ± 19.10
vs 49.59 ± 22.69; P< 0.001) and higher hemoglobin level
(13.91 ± 1.48 vs 13.26 ± 1.61; P< 0.001) than the vitamin
D deficiency group. There were no significant differences
in lipid profile, insulin and HOMR IR between the two
groups.
The prevalence of vitamin D deficiency in various age
groups was illustrated in Fig. 1. The prevalence of vita-
min D deficiency was highest in the participants aged 30
to 39 years (38.4%), and then decreased gradually after
40 years of age reaching the lowest level between 70 to
79 years of age (7.2%). However, the prevalence increased
after 80 years of age (12.4%). The relationships between
vitamin D deficiency and education level are demon-
strated in Fig. 2. The ratios of vitamin D deficiency in-
creased with increasing education level, with the highest
rate observed in those with a graduate degree (31.5%).
The prevalence of vitamin D deficiency also varied by
occupation (Fig. 3), with the lowest prevalence in
farmers (5.4%) and the highest in service industry
workers (22.8%). Overall, the individuals working in agri-
culture, fishery, and manufacturing had a lower preva-
lence of vitamin D deficiency than those working in the
service industry, government employees, and home-
makers (11.4% vs 21.1%, P< 0.001). Figure 4shows the
rates of vitamin D deficiency in the four study districts
in northern Taiwan. Anle district had the highest per-
centage of vitamin D deficiency (21.7%), followed by
Table 1 Baseline characteristics according to the presence or absence of vitamin D deficiency
Normal Vitamin D Deficiency p-value
N 3230 724
Age (years) 56.98 ± 12.18 48.81 ± 12.53 < 0.001*
Male (%) 1253/3230 (38.8) 138/724 (19.1) < 0.001*
25(OH) D (ng/mL) 31.94 ± 8.77 15.49 ± 3.37 < 0.001*
Triglyceride (mg/dL) 118.50 ± 92.53 121.1 6 ± 110.50 0.500
HDL (mg/dL) 57.48 ± 14.98 56.67 ± 14.39 0.187
LDL (mg/dL) 126.90 ± 33.18 123.66 ± 31.94 0.099
Hemoglobin (g/dL) 13.91 ± 1.48 13.26 ± 1.61 < 0.001*
Alkaline P (U/L) 65.88 ± 19.56 63.38 ± 18.98 0.002*
Insulin (uU/mL) 7.91 ± 7.81 8.07 ± 7.25 0.630
HsCRP (mg/L) 2.15 ± 5.24 1.60 ± 2.43 < 0.001*
Creatinine (mg/dL) 0.74 ± 0.18 0.66 ± 0.15 < 0.001*
eGFR (ml/min/1.73 m2) 96.93 ± 21.52 107.93 ± 24.76 < 0.001*
Calcium (mg/dL) 9.36 ± 0.33 9.28 ± 0.33 < 0.001*
Phosphate (mg/dL) 3.81 ± 0.54 3.89 ± 0.51 < 0.001*
Albumin (g/dL) 4.71 ± 0.28 4.68 ± 0.27 0.011*
Hemoglobin A1C (%) 5.78 ± 0.68 5.73 ± 0.78 0.066
IPTH (pg/ml) 43.50 ± 19.10 49.59 ± 22.69 < 0.001*
HOMA IR (units) 2.10 ± 3.01 2.08 ± 2.52 0.915
BMI (kg/m2) 24.65 ± 3.72 23.96 ± 3.99 < 0.001*
Notes: Values are expresse d as mean ± SD or total number (percent)
*pvalue < 0.05
Statistical significance based on the Chi-square test for categorical variables or t-test for continuous variables
Abbreviation: HDL high density lipoprotein-cholesterol, LDL low density lipoprotein-cholesterol, Alkaline P alkaline phosphatase , HsCRP high sensitivity C-reactive
protein,eGFR estimate glomerular filtration rate, IPTH intact parathyroid hormone,HOMA-IR homeostasis model assessment of IR, BMI body mass index
Lee et al. BMC Public Health (2019) 19:337 Page 3 of 8
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Ruifang (19.9%), Gongliao (12.4%), and Wanli (11.1%)
districts.
With regards to the effect of daily diet and behavior
impacting the likelihood of vitamin D deficiency, regular
coffee drinking was associated with a higher prevalence
of vitamin D deficiency than non-consumption of coffee
(20.9% vs 13.9, P< 0.001). In contrast, there was no sig-
nificant difference in vitamin D deficiency between the
individuals who did and did not regularly drink tea
(19.0% vs 16.9%, P= 0.100) or take vitamin D supple-
ments (23.6% vs 18.1%, P= 0.101). In addition, increased
physical activity reduced the likelihood of developing
vitamin D deficiency.
In univariate analysis, many factors were associated
with vitamin D deficiency, so we performed multiple lo-
gistic regression analysis including all factors which
showed that younger age (3040, 4050, 5060, 6070
years), female sex, higher education level (graduate
school, university, senior high school), less physical ac-
tivity, and urban residential area (Anle district) were sig-
nificantly independently associated with vitamin D
deficiency, and that tea consumption was negatively in-
dependently associated with vitamin D deficiency
(Table 2).
Discussion
This study examined 25(OH)-D levels, the prevalence of
vitamin D deficiency and the associated predictors in
healthy adults with normal renal function in northern
Taiwan. To the best of our knowledge, this is the first
study to focus on a large sample of individuals without
CKD. Overall, we found that vitamin D deficiency was
common even in this population, and that the preva-
lence was particularly high in women, those with a
younger age, those who were better educated, and those
who lived in an urban area. In addition, tea consumption
seemed to be a protective factor against vitamin D
deficiency.
In the present study, the mean 25(OH)-D concentra-
tion of the study group was 28.94 ± 10.27 ng/mL and
22.4% had vitamin D deficiency (25(OH)-D concentra-
tion < 20 ng/mL). In the population-based National
Health and Nutrition Examination Survey conducted in
the United States from 2001 to 2006, 32% of the
Fig. 1 The prevalence of 25(OH) vitamin D deficiency in the study
population in different age groups by multivariate analysis (*P< 0.05)
Fig. 2 The prevalence of 25(OH) vitamin D deficiency in the study population in different education levels by multivariate analysis (*P< 0.05)
Lee et al. BMC Public Health (2019) 19:337 Page 4 of 8
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population had a serum 25(OH)-D concentration < 20
ng/mL [21]. In addition, the Korea National Health and
Nutrition Examination Survey conducted in 2008
reported prevalence rates of vitamin D deficiency (< 20
ng/mL) of 47.3% in males and 64.5% in females [22]. In
contrast, in a nationwide population-based study con-
ducted in Thailand, only 5.7% of the population had a
25(OH)-D level < 20 ng/mL [23]. The prevalence rate of
vitamin D deficiency in the current study was lower than
those in the studies from the United States and Korea
but higher than that in the study from Thailand, which
may reflect the effect of latitude. As sun exposure is an
important factor for vitamin D synthesis, people living at
a lower latitude may have more sun exposure and there-
fore a lower prevalence of vitamin D deficiency.
Many studies have demonstrated an increasing preva-
lence of vitamin D deficiency with age [2426]. The
main reason may be that the elderly have decreased con-
centrations of 7-dehydrocholesterol, the precursor of
vitamin D3, and therefore have a decreased ability to
make vitamin D in the skin [27]. However, in the current
study, vitamin D deficiency was less prevalent with ad-
vancing age. Moreover, a young age was a risk factor for
vitamin D deficiency. Some studies have reported that
the elderly use more vitamin D supplements, and this
may explain the higher vitamin D value in the elderly
[28]. However, we found that the elderly subjects in this
study took less vitamin D supplements than the younger
subjects (3039 years old: 34.6%, 4049 years old: 34.8%,
5059 years old: 32.1%, 6069 years old: 27.5%, 7079
years old: 16.8%, > 79 years old: 15.7%; P< 0.001). There-
fore, other factors must contribute to this phenomenon.
The amount of sun exposure is a possible factor. Young
people tend to spend more time indoors for study or
work in Taiwan. In contrast, the elderly may be able to
spend more time outdoors [22,23]. Moreover, young
people may use more sunblock because of cosmetic is-
sues, and therefore have less exposure to the sun [23].
We also investigated the effect of residential district
on vitamin D level, and found that Anle district, which
is an urban area, had a higher proportion of vitamin D
deficiency than Gongliao and Wanli districts, which are
rural areas. This finding is consistent with many other
Fig. 3 The prevalence of 25(OH) vitamin D deficiency in the study population in different occupations by multivariate analysis. Occupation
classification: (a) (Agriculture); (b) (Fishery); (c) (Manufacturing Industry); (d) (Government employee); (e) (Homemaker); (f) (Service
industry) (*P< 0.05)
Fig. 4 The prevalence of 25(OH) vitamin D deficiency in the study
population in different residential districts by multivariate
analysis (*P< 0.05)
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studies [23]. There are several reasons that may explain
the higher proportion of vitamin D deficiency in an
urban area. First, people in urban areas tend to spend
more time indoors due to their jobs and lifestyle. Sec-
ond, air pollution may be a risk factor for vitamin D de-
ficiency, and urban inhabitants are exposed to higher
levels of air pollution than rural inhabitants [11]. How-
ever, according to data from the Central Weather Bureau
of Taiwan, the concentrations of ozone and fine particu-
late matter (PM 2.5) are lower in urban areas than rural
areas. Therefore, lifestyle factors may be the reason why
the residents of the urban area had a higher percentage
of vitamin D deficiency than those in rural areas in the
present study.
Occupation was an important determinant of vitamin
D deficiency in this study, and those who worked in-
doors (including government employees, homemakers,
and service industry workers) had a higher risk of vita-
min D deficiency than those who worked outdoors (in-
cluding agriculture and fishery workers). Education
levels also had a significant impact on vitamin D defi-
ciency, and the subjects with a higher education level
were associated with a higher risk of vitamin D defi-
ciency. This finding is similar to the report by Daly et al.
[25]. However, in the multiple logistic regression analysis
including all factors, education level remained a risk fac-
tor of vitamin D deficiency whereas occupation did not.
This may reflect that the effect of education level was
Table 2 Multiple logistic regression analysis for associations with vitamin D deficiency
Univariate Odds ratio 95% CI Pvalue Multivariate Odds ratio 95% CI Pvalue
Male 0.372 0.3050.453 < 0.001* 0.339 0.2690.429 < 0.001*
Age (years)
3040 Ref. Ref.
4050 0.585 0.4580.747 < 0.001* 0.605 0.4600.795 < 0.001*
5060 0.302 0.2400.381 < 0.001* 0.396 0.3010.520 < 0.001*
6070 0.186 0.1440.241 < 0.001* 0.309 0.2230.430 < 0.001*
7080 0.124 0.0830.187 < 0.001* 0.292 0.1760.484 < 0.001*
> 80 0.227 0.1180.436 < 0.001* 0.662 0.2991.468 0.308
Occupation
Agriculture Ref. Ref.
Fishery 1.019 0.2663.905 0.978 1.460 0.3585.951 0.597
Manufacturing industry 2.637 0.8100.584 0.107 1.666 0.4775.824 0.424
Government employee 4.023 1.22313.226 0.022* 1.496 0.4205.328 0.535
Homemaker 3.936 1.21112.801 0.023* 1.801 0.5166.289 0.357
Service industry 5.226 1.62416.817 0.006* 2.058 0.5947.132 0.255
Education level
Un-educated Ref. Ref.
Primary school 1.050 0.6531.690 0.840 1.065 0.6191.832 0.820
Junior high school 1.276 0.7842.077 0.326 1.051 0.5861.884 0.868
Senior high school 2.629 1.6874.098 < 0.001* 1.944 1.1113.400 0.020*
University 4.298 2.7586.698 < 0.001* 2.706 1.5104.848 0.001*
Graduate school 4.575 2.5528.204 < 0.001* 2.915 1.3906.115 0.005*
Residential district
Anle Ref. Ref.
Gongliao 0.509 0.3860.670 < 0.001* 0.608 0.4390.843 0.003*
Ruifang 0.894 0.7191.113 0.317 1.122 0.8691.450 0.377
Wanli 0.451 0.3480.585 < 0.001* 0.500 0.3730.670 < 0.001*
Coffee (yes) 1.635 1.3681.955 < 0.001* 1.170 0.9431.453 0.154
Tea (yes) 1.155 0.9731.372 0.100 0.755 0.6120.933 0.009*
Physical activity (hours/day) 0.499 0.4100.607 < 0.001* 0.644 0.5220.795 < 0.001*
*pvalue < 0.05.
Statistical significance based on the Chi-square test for categorical variable
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stronger than that of occupation. Education level would
influence the choice of occupation, lifestyle and behavior
factors. Those with a higher education level tend to be
younger, have indoor jobs, and be more concerned about
skin whitening and sun protection [29,30]. In contrast,
those with a lower education level tend to be older, have
outdoor jobs and not care about sun protection.
We also found a relationship between vitamin D defi-
ciency and tea and coffee consumption. To the best of our
knowledge, few studies have investigated this relationship
[31]. Although there was no significant difference in the
prevalence of vitamin D deficiency between those who did
and did not consume tea, tea consumption appeared to be
a protective factor against vitamin D deficiency after mul-
tiple regression analysis adjusting for confounding vari-
ables such as age, education and residential districts. It is
likely that these factors may confound the association
between vitamin D deficiency and tea consumption.
About the influence of age on the association of vitamin
D deficiency and tea consumption, the analysis showed
that the people who consumed tea were younger than
those who did not consume tea (53.05 ± 12.10 vs 59.73 ±
12.50 years; P< 0.001). The younger participants had a
higher prevalence of vitamin D deficiency, which may
have masked the benefit of tea consumption with regards
to 25(OH)-D level. In contrast, coffee consumption was
associated with a higher prevalence of vitamin D defi-
ciency compared to no coffee consumption. However,
coffee consumption was not an independent risk factor
for vitamin D deficiency after multiple logistic regression
analysis, which is consistent with the findings of
Al-Othman A et al. [31]. The mechanism underlying the
positive effect of tea consumption on the 25(OH)-D level
is not entirely clear, and further studies are needed to clar-
ify this relationship.
The strengths of this study are the large study
population and excluding patients with CKD. How-
ever, there are some limitations to the present study.
First, we did not obtain information about dietary in-
take of vitamin D, the amount of sun exposure and
other factors that may have influenced sun exposure,
such as clothing, the amount of time spent outdoors,
the use of sun-screen, and skin color. All of these
factors could affect the 25(OH)-D level. Second, some
of the data such as exercise and tea/coffee consump-
tion were obtained from questionnaires, which may
have introduced reporting or recall bias. Third, we
did not estimate the effect of the season or month of
blood sample collection on vitamin D deficiency.
Fourth,themethodweusedtomeasure25(OH)-D
values (radioimmunoassay) may have resulted in lower
values than the gold standard (liquid chromatography
tandem mass spectrometry), and may have overesti-
mated the prevalence of vitamin D deficiency [32].
Finally, our data were cross-sectional, and thus we
could not analyze longitudinal changes in vitamin D.
Conclusions
In conclusion, our data demonstrated that vitamin D
deficiency is prevalent in northern Taiwan, even in
healthy individuals without CKD. The prevalence was
particularly high in women, those who were younger,
better educated, and who lived in an urban area. Vita-
min D supplements are thus an important issue in
this group of people. Furthermore, we also found that
tea consumption had a protective effect on vitamin D
deficiency. Further studies are needed to confirm our
findings.
Acknowledgements
The authors wish to express their deepest gratitude to all the patients who
participated in this study.
Funding
This investigation was supported by a grant from Chang Gung Medical
Foundation Chang Gung Memorial Hospital, Keelung CMRPG2B01415 and
partially supported by CMRPG2A0433.
Availability of data and materials
The data that support the findings of this study are available from
Community Medicine Research Center, Chang Gung Memorial Hospital,
Keelung, Keelung, Taiwan but restrictions apply to the availability of these
data, which were used under license for the current study, and so are not
publicly available. Data are however available from the authors upon
reasonable request and with permission of Community Medicine Research
Center, Chang Gung Memorial Hospital, Keelung, Keelung, Taiwan.
Authorscontributions
MJL, IWW, CYS, MKT and CCL contributed to the planning of this paper. CCL
and MJL performed the study and conducted the analysis. MJL and HJH
drafted the manuscript. MJL, HJH, IWW, CYS, MKT and HJH contributed to
revisions, read and approved the final manuscript.
Ethics approval and consent to participate
This study was approved by the Institutional Review Board (IRB) of the
Chang Gung Memorial Hospital (IRB No:100-2248A3). All participants agreed
to the study conditions and provided written informed consent before the
enrollment in this study.
Consent for publication
Not applicable
Competing interests
The authors declare that they have no competing interests.
PublishersNote
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published maps and institutional affiliations.
Author details
1
Division of Nephrology, Chang Gung Memorial Hospital, 222 Mai-Chin Road,
Keelung 204, Taiwan.
2
College of Medicine, Chang Gung University,
Tao-Yuan, Taiwan.
3
The Graduate Institute of Clinical Medical Sciences, Chang
Gung University Medical College, School of Medicine, Taoyuan, Taiwan.
4
Division of Endocrinology, Chang Gung Memorial Hospital, Keelung, Taiwan.
Lee et al. BMC Public Health (2019) 19:337 Page 7 of 8
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Received: 21 September 2018 Accepted: 14 March 2019
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... However, the prevalence increases from the age of eighty. The prevalence of vitamin D deficiency reached 7.2% between 70 and 79 years of age and became 12.4% after the age of 80 years old [33]. The highest prevalence of vitamin D deficiency in the 30-39 age group may be because they have a higher average level of education or indoor work and pay more attention to skin whitening and sun protection [33,34]. ...
... The prevalence of vitamin D deficiency reached 7.2% between 70 and 79 years of age and became 12.4% after the age of 80 years old [33]. The highest prevalence of vitamin D deficiency in the 30-39 age group may be because they have a higher average level of education or indoor work and pay more attention to skin whitening and sun protection [33,34]. Vitamin D deficiency occurs in the elderly population due to reduced levels of 7-dehydrocholesterol in the epidermis and reduced kidney function, which reduces vitamin D production [35]. ...
... In addition, lifestyle differences lead to different prevalences of vitamin D deficiency, revealing that older people were more likely to have vitamin D deficiency (<20 ng/mL) than younger people, with prevalence rates of 64.9% and 51.6%, respectively. The prevalence in each group was obviously higher than the prevalence (22.4%) of individuals in Taiwan [33]. This may be because Taiwan has more people supplementing with vitamin D and regularly undergoing health exams. ...
Article
Full-text available
(1) Background: Many studies have revealed a relationship between serum 25-hydroxy vitamin D and physical activity. This study aimed to investigate the relationship between self-reported sitting time and serum 25-hydroxy vitamin D levels in middle-aged and elderly adults in Taiwan. (2) Methods: A total of 396 people were enrolled in our study during a community health examination in Taiwan in 2019. We grouped participants from low to high according to their tertile of serum 25-hydroxy vitamin D levels, using the following categories: deficiency, insufficiency, and sufficiency. Parameters including self-reported sitting time were analyzed between each group. Pearson correlation coefficients were calculated to explore the relationships of serum 25-hydroxy vitamin D levels with age-adjusted risk factors. A scatter plot demonstrated the relationship between serum 25-hydroxy vitamin D levels and self-reported sitting time. The association between serum 25-hydroxy vitamin D levels and self-reported sitting time was assessed by multivariate linear regression with adjustment for age, sex, waist circumference, low-density lipoprotein, triglycerides, and smoking and drinking status. (3) Results: We analyzed the data from 396 participants. A total of 41.4% of participants were male, and the average age of all participants was 64.91 (±8.80) years. The participants in the high serum 25-hydroxy vitamin D group were more likely to have shorter self-reported sitting time. Serum 25-hydroxy vitamin D was negatively correlated (Pearson’s r) with self-reported sitting time, even after adjustment for age. According to the results of multivariate linear regression, vitamin D levels showed a negative association with self-reported sitting time (β = −0.131, p = 0.006) after adjustment for age, sex, waist circumference, low-density lipoprotein, triglycerides, and smoking and drinking status. (4) Conclusions: According to our research, self-reported sitting time was inversely correlated with serum 25-hydroxy vitamin D in middle-aged and elderly people in Taiwan. Meanwhile, longer self-reported sitting time can be an independent risk factor for lower serum 25-hydroxy vitamin D levels.
... The serum level of vitamin D is assessed using 25-hydroxyvitamin D (25 (OH)D), a fat-soluble molecule distributed among the fat tissue, muscle, and liver [5]. Vitamin D levels are also in uenced by age, sex, smoking, sedentary lifestyle, poor dietary habits, sun exposure, sun-protective behavior, latitude of residence, differences in gene expression of vitamin D-metabolizing enzymes, and impaired hepatic 25-hydroxylation [5][6][7][8]. Decreased 25(OH)D levels are closely associated with a variety of illnesses including bone metabolic disorders, tumors, cardiovascular diseases, diabetes mellitus, arterial hypertension, heart failure, peripheral arterial disease, acute myocardial infarction, various types of cancers, autoimmune and in ammatory diseases, decreased immune defenses and increased mortality [9,10]. The vitamin D receptor was found in β cells in the pancreas, adipose, and musculoskeletal tissues and vitamin D inadequacy could compromise the capacity of β cells to convert pro-insulin into insulin [4]. ...
... These factors are consistent with those reported in previous publications. Risk factors such as female sex, young people, and higher education attainment were reported in one US adult -based report and two Taiwanese adult-based studies, and their associations with VDI were comprehensively discussed from several aspects including lifestyle, occupation, physical activity, residency location, sun exposure, and metabolic difference [7,30,43]. Furthermore, the correlation between high serum LDL levels and VDI was elucidated by the regulation of lipid metabolism, including the inhibition of lipogenesis and increased lipolysis via vitamin D-mediated calcium spillage into fat cells and pancreatic islet function in the previous studies [44][45][46][47]. ...
Preprint
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Background The association between vitamin D insufficiency (VDI) and metabolic syndrome (MetS) remains unclear. Little information is available regarding the association between the VDI and health-related quality of life (HRQoL) in the health belief model (HBM). This study aimed to investigate the association between the VDI, HBM, HRQoL, and MetS in community-based Taiwanese adults. Methods This cross-sectional study recruited 1015 Taiwanese patients aged ≥ 30 years between August 2019 and December 2021. Sociodemographic data, anthropometric variables, and vitamin D levels, defined as 25 (OH) D concentrations, were acquired from medical records and physical examinations. Data regarding health beliefs and HRQoL were obtained using a questionnaire. Results The mean 25(OH)D concentration was 29.59 ± 10.80 ng/mL and the overall prevalence of VDI was MetS was 54.9%. There was no significant difference in the incidence of MetS between the VDI and sufficiency groups. Multivariate analysis revealed that the risk factors associated with VDI development were female sex, age < 65 years, college and above education attainment, high LDL concentration, no alcohol use, and low scores on the emotional role item of HRQoL. There was no association between the VDI and HBM. In people with VDI, age, smoking, education level, blood pressure, perceived barriers, and self-efficacy in the HBM were correlated with HRQoL. Conclusions The VDI was not correlated with MetS incidence or HBM. Risk factors including age, female sex, education level, serum LDL concentration, alcohol use, and role-emotional items of HRQoL could be integrated into health initiative programs to reduce the risk of VDI.
... Most countries have national screening programs for measuring vitamin D levels in the general population or selected risk groups [1,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51]. ...
... One of the significant results of our study is a higher prevalence of vitamin D deficiency in women (29.4%) in comparison with men (20.2%). Several studies also report higher prevalence in women [31,44,47], whereas some found dominance in men [39,45] and others found no sex-dependent differences [59]. A study in Germany found a higher prevalence of vitamin D deficiency in men during autumn and in women during winter, a result that is also supported by our study (12.53 times higher odds for vitamin D deficiency in men in October in comparison with August) [60]. ...
Article
Full-text available
Background: Vitamin D deficiency is recognized as a general health condition globally and is acknowledged as a public health concern in Europe. In Romania, a national program of examination of the status of vitamin D for high-risk groups has demonstrated a vitamin D deficiency prevalence of 39.83%. No national data on the status of vitamin D in the general adult population are available to date. Methods: We used the framework of the European Health Examination Survey to analyze vitamin D levels in a sample population of adults aged 25–64 years, from 120 family doctors’ patients lists, by using a sequential sampling method. Data were weighted to the Romanian population. Vitamin D deficiency was defined as 25(OH)D < 20 ng/mL. Results: In total, 5380 adults aged 25–64 years were included in this study. The overall prevalence of vitamin D deficiency is 24.8%. Predictors of vitamin D deficiency were found to be obesity, female sex, living in rural areas, lower education level, and lower socioeconomic status. Conclusions: Specific recommendations for vitamin D screening and supplementation should be issued for women by specialist boards. Further studies are needed to identify seasonal variation and to establish a correlation with nutritional surveys.
... Our study revealed a mean vitamin D concentration 22.2 ± 8 ng/mL and 42.5% of our population with vitamin D deficiency. In a study of vitamin D deficiency among a healthy adult population in northern Taiwan, the mean vitamin D concentration was 28.9 ng/mL, and 22.4% of the study population had vitamin D deficiency 42 . Several co-factors, including diet, outdoor activity, use of sunscreen lotion, percentage of sunny/ www.nature.com/scientificreports/ ...
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Vitamin D deficiency is common in patients with inflammatory bowel disease (IBD). In this study, we aimed to evaluate the prevalence and risk factors of vitamin D deficiency in a Taiwanese IBD cohort. Vitamin D levels were checked in adult patients with IBD who were treated at Changhua Christian Hospital, a medical center in central Taiwan, from January 2017 to December 2023. The risk factors for vitamin D deficiency were evaluated. 106 adult IBD patients were included, including 20 patients with Crohn’s disease and 86 with ulcerative colitis. The median age at diagnosis was 39.2 years. The mean vitamin D level was 22.2 ± 8 ng/mL. Forty-five patients (42.5%) had vitamin D deficiency (vitamin D level < 20 ng/mL). Comparing patients with normal vitamin D levels and those with vitamin D deficiency after multivariate adjustment, female sex and early age at diagnosis were identified as statistically significant risk factors. We found a prevalence of 42.5% of vitamin D deficiency in the Taiwanese IBD population. Understanding this issue is essential for teaching patients and doctors about vitamin D deficiency screening and improving patient outcomes.
... • Female sex. • Vitamin D levels below 20 ng/ml, as per established guidelines [12], and Presence of insulin resistance, indicated by HOMA-IR levels between 1.82 and 3.63 [13]. ...
... In Taiwan, a study among community-based older persons found most of the deficiency in Vit. D was 22.4% as serum 25(OH)D which was <20 ng/mL, and the mean level of participants was <30 ng/mL [39]. Unfortunately, there is limited study of awareness among nursing home dwellers in Taiwan to evaluate the prevalence of Vit. ...
Article
Full-text available
The purpose of this study was to compare the effects of nutritional supplement drinks (NSDs) and nutritional education (NE) on the nutritional status and physical performance of older nursing home residents who were at risk of malnutrition. This study was a clustered, randomized, parallel, multi-center clinical trial, with 107 participants more than 65 years old and at risk of malnutrition recruited from several nursing homes in this study. Participants were divided into two groups: an NE group (n = 50) and an NSD group (n = 57). The NE group was given NE by a dietitian, while the NSD group was provided with two packs of NSD except receiving NE (Mei Balance, Meiji Holdings, Tokyo, Japan) per day as a snack between meals and before bed. Anthropometric data, blood pressure, nutritional status, blood biochemical biomarkers, and physical performance were measured before and after 12-week interventions. After 12 weeks of NE combined with NSD intervention, body weight, body-mass index, the mini nutritional assessment-short form (MNA-SF) score, walking speed, and SF-36 questionnaire score were improved in older nursing home residents at risk of malnutrition.
Article
This study aimed to compare the efficacy of shorter vs. longer tenofovir disoproxil fumarate (TDF) prophylaxis in preventing hepatitis B virus (HBV) relapse in cancer patients with chronic hepatitis B (CHB) undergoing chemotherapy. This phase IV, prospective randomized trial enrolled cancer patients with CHB from 2014 to 2019 in Taiwan. Included patients were randomized to receive either 24- (Arm A) or 48-week (Arm B) post-chemotherapy TDF and compared for cumulative incidence of virological and clinical relapse. Logistic regressions were conducted to determine the factors associated with HBV relapse. One hundred patients were randomized, and 41 patients in Arm A and 46 in Arm B completed the TDF treatment. No significant difference was found in cumulative incidence of virological relapse (Arm A: 94.4%, Arm B: 93.1%, p = 0.110) or clinical relapse among patients with baseline HBV DNA > 2000 IU/mL (Arm A: 38.9%, Arm B: 26.7%, p = 0.420) between the two arms. High baseline HBV DNA ≥ 10,000 IU/mL (OR = 51.22) and HBsAg ≥ 1000 IU/mL (OR = 8.64) were independently associated with an increased virological relapse. Alanine aminotransferase (ALT), serum phosphorus, vitamin D, and estimated glomerular filtration rate (eGFR) remained stable throughout the study. The 24-week preventative TDF has comparable efficacy to the 48-week treatment in virologic and clinical relapse. High baseline HBsAg or HBV DNA is associated with a higher risk of HBV relapse. These findings imply a 24-week duration of TDF treatment with a close monitor for patients with a high baseline viral load. Hepatitis B virus infection is a prominent cause of liver cancer and chronic liver disease and affected millions of people worldwide. When HBV-infected people are exposed to immunosuppressive medication or chemotherapy for cancer, the chance of HBV reactivation rises considerably. This trial showed 24-week tenofovir disoproxil fumarate (TDF) may be sufficient for preventing HBV relapse in cancer patients receiving chemotherapy. NCT02081469.
Article
Full-text available
Objective Vitamin D deficiency in a patient with autoimmune rheumatic disease is the most discussed topic these days, is considered to be a pandemic, and its prevalence and associations have been studied by many countries. We aim to study the prevalence of vitamin D deficiency in autoimmune rheumatic diseases in patients visiting the rheumatology clinic at the Jigme Dorji Wangchuck National Referral Hospital in Thimphu. Methods A descriptive study was conducted on 126 patients in Jigme Dorji Wangchuck National Referral Hospital, who were visiting the rheumatology clinic. Vitamin D levels were analysed among these rheumatology patients. EpiData software is used for data entry and analysis. Results Out of 126 patients, 71 had rheumatoid arthritis, 34 had systemic erythema-tosus, 8 mixed connective tissue disease and 13 had other autoimmune rheumatic diseases. Among these, only 12 (9.52%) patients had normal vitamin D levels, and 114 (90.5%) patients had lower than normal serum levels of the vitamin. Among these, 75 (59.5%) were deficient and 39 (31.0%) were insufficient. Conclusion The study found that the prevalence of Vitamin D deficiency is high with 59.5% among patients with autoimmune rheumatic diseases and only with 9.5% were with normal levels of vitamin D.
Article
Full-text available
Objective To establish the impact the chronic kidney disease stage has in the native vitamin D levels in patients not undergoing dialysis treatment. Methods A study performed in Manizales, Colombia, a city located 2,200 meters above sea level, without important stational variations. Patients with 18 years of age or more, with chronic kidney disease stages 2 to 5 and not undergoing dialysis treatment were recruited for this study. Demographic and anthropometric variations were evaluated as well as solar exposure, CKD etiology and laboratory variables related to bone and mineral diseases. For each CKD clinical stage, correlations were evaluated for vitamin D levels, laboratory results for bone and mineral diseases, solar exposure and ethnicity. Results Three hundred thirty-three patients were evaluated with a median age of 71 years, most of them mestizo (71%), 173 were women. The main CKD etiology was hypertensive nephropathy (32.2%). 21.1% of patients had normal vitamin D levels, 70.1% were within insufficient range and 8.8% were in deficit. A negative correlation was found between the levels of vitamin 25 (OH) D and the values for: creatinine, phosphorous, calcium x phosphorous product, PTH, 24 hours urine protein and BMI. A positive relationship was found for calcium and albumin. Positive significant statistical correlation was found for vitamin 25(OH) D levels and solar exposure for stages 3b and 4 of CKD. Conclusions It is common to find low levels of vitamin 25(OH) D in patients with CKD; these can contribute to the appearance of secondary hyperparathyroidism.
Article
Full-text available
Objective To establish the impact the chronic kidney disease stage has in the native vitamin D levels in patients not undergoing dialysis treatment. Methods A study performed in Manizales, Colombia, a city located 2,200 meters above sea level, without important stational variations. Patients with 18 years of age or more, with chronic kidney disease stages 2 to 5 and not undergoing dialysis treatment were recruited for this study. Demographic and anthropometric variations were evaluated as well as solar exposure, CKD etiology and laboratory variables related to bone and mineral diseases. For each CKD clinical stage, correlations were evaluated for vitamin D levels, laboratory results for bone and mineral diseases, solar exposure and ethnicity. Results Three hundred thirty-three patients were evaluated with a median age of 71 years, most of them mestizo (71%), 173 were women. The main CKD etiology was hypertensive nephropathy (32.2%). 21.1% of patients had normal vitamin D levels, 70.1% were within insufficient range and 8.8% were in deficit. A negative correlation was found between the levels of vitamin 25 (OH) D and the values for: creatinine, phosphorous, calcium x phosphorous product, PTH, 24 hours urine protein and BMI. A positive relationship was found for calcium and albumin. Positive significant statistical correlation was found for vitamin 25(OH) D levels and solar exposure for stages 3b and 4 of CKD. Conclusions It is common to find low levels of vitamin 25(OH) D in patients with CKD; these can contribute to the appearance of secondary hyperparathyroidism.
Article
Full-text available
Recreational sun exposure accounts for a large number of acute and chronic dermatological diseases, including skin cancer. This study aimed at estimating the one-year prevalence of sun exposure and skin health-associated knowledge and attitudes among Austrian citizens. The population-based UVSkinRisk survey investigated a representative sample of Austrian adults using a structured questionnaire. In total, 1500 study subjects (median age 33.0 years, 50.5% females) participated in this questionnaire survey. Among study participants, prevalence of sun exposure was 47%, with slightly higher rates in males (48%) compared to females (46%). Younger age, lower professional category, darker skin type, motives to tan, sunbed use, sunburn, and outdoor sport activity increased the odds for prevalent sun exposure. This is the first population-based study evaluating the prevailing sun exposure and recreational habits influencing skin health among Austrian citizens. Despite public media campaigns educating on the harmful effects of sunlight exposure, we found a high prevalence of self-reported sunlight exposure. The results suggest that multifaceted socio-cultural characteristics stimulate recreational sun exposure and tanning habits. Communicating individualized Public (Skin) Health messages might be the key to prevent photo-induced skin health hazards in light-skinned populations. The practical and theoretical implications of these findings are discussed. Keywords: public health; preventive medicine; sunlight exposure; photo-protective behavior
Article
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Vitamin D deficiency is a major public health problem worldwide. However, most countries are still lacking data, particularly in infants, children, adolescents and pregnant women. The objective of the present report was to conduct a more recent systematic review of global vitamin D status, with particular emphasis in at risk groups. A systematic review was conducted between April and June of 2013 to identify articles on vitamin D status worldwide published in the last 10 years in apparently healthy individuals. Only studies with vitamin D status prevalence were included. If available, the first source selected was population-based or representative samples studies. Clinical trials, case-control studies, case reports or series, reviews, validation studies, letters, editorials, or qualitative studies were excluded. A total of 98 articles were eligible and included in the present report. Prevalence of vitamin D status was reported by continent. In areas with available data, the prevalence of low vitamin D status is a global problem in all age groups, in particular in girls and women from the Middle East. These results also evidenced the regions with missing data for each specific population groups, such as in infants, children and adolescents worldwide, and in most countries of South America and Africa. In conclusion, vitamin D deficiency is a global public health problem in all age groups, particularly in those from the Middle East.
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To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with mortality from cardiovascular, cancer, or other conditions, under various circumstances. Systematic review and meta-analysis of observational studies and randomised controlled trials. Medline, Embase, Cochrane Library, and reference lists of relevant studies to August 2013; correspondance with investigators. Observational cohort studies and randomised controlled trials in adults, which reported associations between vitamin D (measured as circulating 25-hydroxyvitamin D concentration or vitamin D supplement given singly) and cause specific mortality outcomes. Data were extracted by two independent investigators, and a consensus was reached with involvement of a third. Study specific relative risks from 73 cohort studies (849 412 participants) and 22 randomised controlled trials (vitamin D given alone versus placebo or no treatment; 30 716 participants) were meta-analysed using random effects models and were grouped by study and population characteristics. In the primary prevention observational studies, comparing bottom versus top thirds of baseline circulating 25-hydroxyvitamin D distribution, pooled relative risks were 1.35 (95% confidence interval 1.13 to 1.61) for death from cardiovascular disease, 1.14 (1.01 to 1.29) for death from cancer, 1.30 (1.07 to 1.59) for non-vascular, non-cancer death, and 1.35 (1.22 to 1.49) for all cause mortality. Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements. In randomised controlled trials, relative risks for all cause mortality were 0.89 (0.80 to 0.99) for vitamin D3 supplementation and 1.04 (0.97 to 1.11) for vitamin D2 supplementation. The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics. However, for vitamin D2 supplementation, increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods. Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease, cancer, and other causes. Supplementation with vitamin D3 significantly reduces overall mortality among older adults; however, before any widespread supplementation, further investigations will be required to establish the optimal dose and duration and whether vitamin D3 and D2 have different effects on mortality risk.
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Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with mortality from cardiovascular, cancer, or other conditions, under various circumstances. Design Systematic review and meta-analysis of observational studies and randomised controlled trials. Data sources Medline, Embase, Cochrane Library, and reference lists of relevant studies to August 2013; correspondance with investigators. Study selection Observational cohort studies and randomised controlled trials in adults, which reported associations between vitamin D (measured as circulating 25-hydroxyvitamin D concentration or vitamin D supplement given singly) and cause specific mortality outcomes. Data extraction Data were extracted by two independent investigators, and a consensus was reached with involvement of a third. Study specific relative risks from 73 cohort studies (849 412 participants) and 22 randomised controlled trials (vitamin D given alone versus placebo or no treatment; 30 716 participants) were meta-analysed using random effects models and were grouped by study and population characteristics. Results In the primary prevention observational studies, comparing bottom versus top thirds of baseline circulating 25-hydroxyvitamin D distribution, pooled relative risks were 1.35 (95% confidence interval 1.13 to 1.61) for death from cardiovascular disease, 1.14 (1.01 to 1.29) for death from cancer, 1.30 (1.07 to 1.59) for non-vascular, non-cancer death, and 1.35 (1.22 to 1.49) for all cause mortality. Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements. In randomised controlled trials, relative risks for all cause mortality were 0.89 (0.80 to 0.99) for vitamin D3 supplementation and 1.04 (0.97 to 1.11) for vitamin D2 supplementation. The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics. However, for vitamin D2 supplementation, increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods. Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease, cancer, and other causes. Supplementation with vitamin D3 significantly reduces overall mortality among older adults; however, before any widespread supplementation, further investigations will be required to establish the optimal dose and duration and whether vitamin D3 and D2 have different effects on mortality risk.
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