Handgrip strength, ageing and mortality in rural Africa

Abstract

Background: muscle strength measured as handgrip strength declines with increasing age and predicts mortality. While handgrip strength is determined by lifestyle through nutrition and physical activity, it has almost exclusively been studied in western populations with a sedentary lifestyle. This study aims to investigate the relation between handgrip strength, ageing and mortality in a population characterised by a predominance of malnutrition and manual labour.
Design: a population-based longitudinal study.
Setting: a traditional African rural population in Ghana.
Subjects: nine hundred and twenty-three community-dwelling individuals aged 50 and older.
Methods: demographic characteristics were registered. At baseline, height, body mass index (BMI) and handgrip strength were measured and compared with those in a western reference population. Survival of the participants was documented during a period of up to 2 years.
Results: handgrip strength was dependent on age, sex, height and BMI. Compared with the western reference population, handgrip strength was lower due to a lower height and BMI but declined over age similarly. Risk of mortality was lower in participants having higher handgrip strength, with a hazard ratio of 0.94 per kg increase (P = 0.002). After adjustment for age, sex, tribe, socio-economic status, drinking water source, height and BMI, only handgrip strength remained predictive of mortality.
Conclusion: in a traditional rural African population characterised by malnutrition and manual labour, handgrip strength declines over age and independently predicts mortality similar to western populations. Handgrip strength can be used as a universal marker of ageing.

Full text

Age and Ageing 2015; 44: 465–470
doi: 10.1093/ageing/afu165
Published electronically 20 October 2014
© The Author 2014. Published by Oxford University Press on behalf of the British Geriatrics Society.
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Handgrip strength, ageing and mortality
in rural Africa
JACOB J. E. KOOPMAN1,2 ,DAVID VAN BODEGOM1,2,DIANA VAN HEEMST1,2,3,
RUDI G. J. WESTENDORP1,2
1
Department of Gerontology and Geriatrics, Leiden University Medical Center, Post Box 9600, Leiden 2300 RC, The Netherlands
2
Leyden Academy on Vitality and Ageing, Leiden 2333 AA, The Netherlands
3
Netherlands Consortium for Healthy Ageing (NCHA), Leiden University Medical Center, Post Box 9600, Leiden 2300 RC,
The Netherlands
Address correspondence to: J. J. E. Koopman. Tel: (+31) 71 5266640; fax: (+31) 71 5266912. Email: j.j.e.koopman@lumc.nl
Abstract
Background: muscle strength measured as handgrip strength declines with increasing age and predicts mortality. While hand-
grip strength is determined by lifestyle through nutrition and physical activity, it has almost exclusively been studied in western
populations with a sedentary lifestyle. This study aims to investigate the relation between handgrip strength, ageing and mortal-
ity in a population characterised by a predominance of malnutrition and manual labour.
Design: a population-based longitudinal study.
Setting: a traditional African rural population in Ghana.
Subjects: nine hundred and twenty-three community-dwelling individuals aged 50 and older.
Methods: demographic characteristics were registered. At baseline, height, body mass index (BMI) and handgrip strength
were measured and compared with those in a western reference population. Survival of the participants was documented
during a period of up to 2 years.
Results: handgrip strength was dependent on age, sex, height and BMI. Compared with the western reference population,
handgrip strength was lower due to a lower height and BMI but declined over age similarly. Risk of mortality was lower in parti-
cipants having higher handgrip strength, with a hazard ratio of 0.94 per kg increase (P= 0.002). After adjustment for age, sex,
tribe, socio-economic status, drinking water source, height and BMI, only handgrip strength remained predictive of mortality.
Conclusion: in a traditional rural African population characterised by malnutrition and manual labour, handgrip strength
declines over age and independently predicts mortality similar to western populations. Handgrip strength can be used as a uni-
versal marker of ageing.
Keywords: handgrip strength, ageing, mortality, Africa, older people
Introduction
Muscle strength measured as handgrip strength is widely
used as a simple and robust marker of ageing. Handgrip
strength declines with increasing age in different ethnicities,
especially after the age of 50 [1,2,3,4,5,6,7]. At both
middle and high ages, low handgrip strength is associated
with increased risks of future disability [8, 9, 10, 11,12,13,
14]; of age-related diseases such as the metabolic syndrome
[15], cardiovascular disease [16, 17], type 2 diabetes mellitus
[18] and cognitive impairment [12,19]; of hospitalisation [13,
20] and of treatment-related complications [13]. Moreover,
low handgrip strength predicts all-cause mortality [13,14,15,
21,22,23] as well as mortality due to cardiovascular disease
465

[6,24] and cancer [15,23,24]. Consequently, low handgrip
strength is considered as an accurate indicator of frailty [25].
Apart from age, sex and ethnicity, handgrip strength is de-
pendent on height, body mass index (BMI), nutritional status
and physical exercise [11,26,27,28,29]. While these deter-
minants are closely related to lifestyle, research on handgrip
strength has almost exclusively been conducted in western
societies where an affluent and sedentary lifestyle is omnipre-
sent [3, 30,31]. In societies characterised by a predominance
of malnutrition and manual labour, handgrip strength might be
areflection of dietary composition and muscle training rather
than ageing. In addition, the association between handgrip
strength, ageing and mortality might be mediated by age-related
diseases and attenuated when these are uncommon [27,32].
This study investigates the relation between handgrip
strength, ageing and mortality in a traditional rural African
population where a sedentary lifestyle is absent and age-related
diseases are uncommon [32, 33, 34]. We show how handgrip
strength is distributed over age and compare this distribution
with its distribution in a western reference population; we
assess the individual characteristics that determine handgrip
strength and we assess whether handgrip strength predicts
mortality in this population.
Methods
Setting and participants
This study was conducted in the Garu-Tempane District in
the Upper East Region in Ghana. The area is rural, remote
and one of the least developed in the country. The vast
majority of the inhabitants are involved in non-commercial
agriculture performed by manual labour without proper
means of transportation or mechanised farming. Hospital
care is absent. Infectious diseases are highly endemic and
constitute the main causes of death, although the prevalence
of human immunodeficiency virus (HIV) is low (<4%) com-
pared with other African regions [35].
Since 2002, we have kept a demographic registry of the
population within a research area of 375 km
2
comprising 32
villages. During yearly visits, we registered the name, age, sex,
tribe and location of living of each inhabitant. In 2007, we deter-
mined the property value of each household. From this value,
an index of the socio-economic status with a standard normal
distribution was calculated according to the Demographic and
Health Survey method [36]. In addition, we registered the main
drinking water source of each household. Water from boreholes
was classified as safe and water from open wells and rivers as
unsafe, based on their pathogen contents [37]. Annual migra-
tion relative to the study population’s size was 2% into and 1%
out of the research area. An elaborate description of this study
population has been given elsewhere [32, 34, 36, 37].
Ethical approval was given by the Ethical Review Committee
of Ghana Health Services, the Committee Medical Ethics of
the Leiden University Medical Center, and the local chiefs and
elders. Because of illiteracy, informed consent was obtained
orally from the participants after explanation of the purpose
and conduction of this research project. Participation was
only proceeded after verbal consent in the participant’sown
language.
Measurements
In 2009 and 2010, we measured handgrip strength among
923 inhabitants aged 50 and older, who were recruited in vil-
lages visited consecutively. To ensure maximal participation,
we set up a mobile field work station in the villages and, if ne-
cessary, brought less mobile participants by car. Reasons of
exclusion included death of the individual since the last regis-
tration (n= 48), refusal of participation (n= 35), absence
from the research area during our visits because of migration
or travelling (n= 30) and other reasons (n= 46).
Handgrip strength in kilograms was measured using a
calibrated Jamar hand dynamometer (Sammons Preston Inc.,
Bolingbrook, IL, USA), while the participant was standing in
an upright position with the arms unsupported parallel to the
body. The width of the dynamometer’s handle was adjusted
to each participant’s hand size. Participants were instructed
to exert maximal force with each hand once. The handgrip
strength of the hand with the highest measurement was regis-
tered. Body height and weight were measured with a calibrated
length scale and weighing scale. BMI was calculated as body
weight in kilograms divided by squared body height in metres.
After the measurements in 2009 and 2010, follow-up
data on 915 individuals (99.1%) were available in our demo-
graphic registry. Follow-up lasted until death, migration out
of the research area, loss to follow-up or our last visit to the
research area in 2011.
Reference population
To compare the Ghanaian study population with a western
population, we retrieved data from the Leiden Longevity
Study. This study included offspring of long-lived native
Dutch siblings and the partners of the offspring without
selection criteria on health or demographic characteristics.
The design of the study has been previously described in
more detail [38]. We used data on age, sex, height, BMI and
handgrip strength measured in 316 offspring and 311 part-
ners aged 50–80. Handgrip strength did not differ between
offspring and partners. The measurements were performed
with the same hand dynamometer and in the same position
as described for the Ghanaian study population [39].
Analyses
Differences between both populations in mean values of
height, BMI and handgrip strength and in the decline in hand-
grip strength per year of age were determined by linear regres-
sion with age as an independent variable and were restricted to
participants aged 50–80. Determinants of handgrip strength
in the Ghanaian study population were assessed by linear
regression including all participants aged 50–97. Handgrip
strength in the Ghanaian study population was standardised
according to the age group- and sex-specific mean height and
466
J. J. E. Koopman et al.

BMI in the Dutch reference population, using the regression
coefficients obtained for these determinants in the Ghanaian
study population. To investigate whether handgrip strength
predicted mortality, we constructed Kaplan–Meier survival
curves with left truncation to account for different ages at
baseline. Survival curves were separated between individuals
classified as having low or high handgrip strength according to
the age group- and sex-specific median. Hazard ratios were
determined by Cox regression with follow-up starting at the
time of the measurements of handgrip strength.
Results
Table 1shows the baseline characteristics of the Ghanaian
study population at the moment of handgrip strength meas-
urement in 2009 or 2010. For comparison, we used data
from a Dutch reference population including 316 males and
311 females aged 50–80. As described previously for this
population [39], mean height (standard deviation) was 177.9 cm
(7.7) in males and 165.7 cm (5.9) in females; mean BMI was
27.1 (4.1) in males and 26.4 (4.6) in females and mean hand-
grip strength was 46.9 kg (8.1) in males and 29.3 kg (5.5) in
females. These values of height and BMI were higher than
those in the Ghanaian study population (both P< 0.001)
adjusted for age.
Figure 1A shows that mean handgrip strength was lower
in the Ghanaian study population compared with the Dutch
reference population. Overall, the difference (95% confi-
dence interval) was 14.7 kg (13.6–15.8) in males and 5.7 kg
(4.9–6.4) in females (both P< 0.001). In the Ghanaian study
population, handgrip strength declined with 0.4 kg per year
of age (0.3–0.5) in males and with 0.3 kg per year of age
(0.2–0.4) in females (both P< 0.001). For comparison, hand-
grip strength in the Dutch reference population declined
with a slightly higher rate of 0.6 kg per year of age (0.5–0.7)
in males up to the age of 80 (P= 0.046), with a similar rate in
males up to the age of 75 years (P= 0.384) and with a similar
rate in females (P= 0.687).
Determinants of handgrip strength in the Ghanaian study
population are described in the Supplementary data, Table S2
available in Age and Ageing online. In a multivariate analysis of
demographic and anthropometric characteristics, handgrip
strength in both sexes was higher in individuals with a higher
age, with a higher height and with a higher BMI. When this
analysis was not stratified by sex, handgrip strength was 6.0
kg (5.0–7.0) higher in males (P< 0.001).
Figure 1B shows that the differences in handgrip strength
between the Ghanaian study population and the Dutch refer-
ence population were attenuated when handgrip strength in
........................................
Table 1. Baseline characteristics of the Ghanaian study
population
Males Females
Individuals, n480 443
Age, median (IQR) years 67 (58–76) 61 (56–70)
Tribe, %
Bimoba 69.5 68.6
Kusasi 22.5 25.5
Other 8.1 5.9
Household property value, median
(IQR) US$
1,008 (500–1,700) 1,196 (583–2,108)
Access to safe drinking water, % 86.7 88.5
Weight, kg 50.6 (7.9) 45.5 (7.6)
Height, cm 167.5 (6.8) 157.9 (6.8)
BMI, kg/m
2
18.0 (2.3) 18.2 (2.6)
Handgrip strength, kg 31.3 (8.7) 23.6 (5.9)
Data are presented as means with standard deviations unless specified
otherwise.
IQR, interquartile range; BMI, body mass index.
Figure 1. Handgrip strength per sex and per age group in the
Ghanaian study population compared with the Dutch reference
population. (A) A comparison of mean handgrip strength with
95% confidence intervals per 5-year age category and per sex as
observed in the Ghanaian study population and the Dutch ref-
erence population [39]. (B) Idem after standardisation of the
individual handgrip strength measurements in the Ghanaian
study population according to the age group- and sex-specific
height and BMI of the Dutch reference population [39].
467
Handgrip strength, ageing and mortality in Africa

the Ghanaian study population was standardised according
to the age group- and sex-specific mean height and BMI of
the Dutch reference population. Hereby accounting for the
differences in height and BMI between both populations,
handgrip strength was similar in males (P= 0.350) and 1.7 kg
(0.9–2.4) higher in Ghanaian females (P< 0.001). Standardised
handgrip strength declined with similar rates over age in males
(P= 0.067) and females (P= 0.233) in both populations.
Figure 2shows how mortality is predicted by handgrip
strength in the Ghanaian study population. Data on follow-
up were available for 476 males and 439 females. From the
baseline measurements in 2009 and 2010 through the end of
follow-up in 2011, we recorded 1,492 person-years and 46
deaths. Mean individual follow-up was 20 months (6).
Individuals were classified as having low or high handgrip
strength according to the age group- and sex-specific median.
Risk of mortality was lower in individuals with high handgrip
strength, with a hazard ratio of 0.45 (P= 0.010) adjusted for
age and sex.
Determinants of mortality in the Ghanaian study popula-
tion are described in the Supplementary data, Table S3 avail-
able in Age and Ageing online. While handgrip strength, age and
BMI determined mortality in the univariate analysis, only
handgrip strength determined mortality in the multivariate
analysis with a hazard ratio of 0.94 per kg increase (P=0.016).
The association between handgrip strength and mortality in
the univariate analysis remained unchanged after the adjust-
ments in the multivariate analysis. In the multivariate analy-
sis, the association of handgrip strength with mortality was
not different between individuals below or above the age
of 65 (P= 0.920), between males and females (P= 0.380),
between individuals with a low or high BMI (P= 0.188) or
between individuals with a low or high socio-economic status
(P= 0.890).
Additional adjustment for family relations by clustering
on the household level did not materially change the results.
Discussion
This study aims to study the relation between handgrip
strength, ageing and mortality in a traditional rural African
population with a non-western lifestyle. Handgrip strength
was lower compared with a western reference population due
to a lower height and BMI, but it declined with a similar rate
over age. Lower levels of handgrip strength predicted mortality
independent of its other determinants related to nutritional
and socio-economic status. Its predictive value was compar-
able with that known for western populations [6,13,21,24].
The Ghanaian study population contrasts sharply with
western populations, as a sedentary lifestyle is absent and
age-related diseases are uncommon [32, 33, 34]. Because
handgrip strength is dependent on nutritional status [29],
this contrast is most relevantly characterised by a low
BMI and near absence of obesity [32]. In line with this, hand-
grip strength was closely related to BMI and low compared
with a Dutch reference population due to a lower BMI.
Besides nutrition, handgrip strength is associated with phys-
ical activity and socio-economic status [26,27,40,41,42].
Unlike western populations, almost all inhabitants in the re-
search area engage in lifelong physical exercise. Manual
labour in farming and housekeeping is necessary for subsist-
ence up to the highest ages. Meanwhile, mechanical means of
farming and transportation are lacking. Most inhabitants live
in poverty [33], and common property is confined to cattle,
fertiliser and iron roofing [36]. Despite these differences, the
variation in handgrip strength in the Ghanaian study popula-
tion was similar to that in the Dutch reference population
and as reported for other western populations [2,43,44].
Moreover, handgrip strength declined over age in these
populations similarly.
Few other studies have described handgrip strength in trad-
itional lean populations in Africa. Absolute levels of hand-
grip strength have been reported to be up to 4 kg lower in
rural Kenya, rural Malawi and among refugees from Rwanda
compared with those found at similar ages in the Ghanaian
study population [31,45,46]. Handgrip strength in these
populations was also, though less, dependent on BMI. The
decline in handgrip strength over age was similar to that in the
Ghanaian study population. In a population-wide study in
South Africa, handgrip strength did not differ between ethnici-
ties or between rural and urban areas, but it was associated
with age, anthropometry and health [30]. None of these
studies related handgrip strength with mortality.
As a western reference population, we used the Leiden
Longevity Study [39]. Handgrip strength in this study is
slightly higher compared with other western populations.
Figure 2. Handgrip strength as a predictor of mortality in the
Ghanaian study population. Age-specific survival is dependent
on handgrip strength in the Ghanaian study population.
Handgrip strength is classified as low or high according to the
age group- and sex-specific medians. The hazard ratio (HR) is
given for individuals with high handgrip strength relative to
those with low handgrip strength, adjusted for age and sex.
468
J. J. E. Koopman et al.

This difference can be a result of international variations in
the level of handgrip strength, while the declines over age
are similar [4]. Alternatively, this difference can be a result
of variations in body position during the measurements.
Body position influences the estimation of handgrip strength,
although it is not likely to influence its decline over age or its
relation with mortality [47, 48, 49, 50]. When using reference
data from a meta-analysis of handgrip strength in 12 western
study populations with a body position different from the
Leiden Longevity Study, the decline in handgrip strength
over age was similar to that in the Ghanaian study population
[7]. Suitably, the body position during the measurements in
the Ghanaian study population was identical to that in the
Leiden Longevity Study.
This study has the following limitations. First, handgrip
strength was measured only once, while it might have been
valuable to relate individual changes in handgrip strength
over age with anthropometry and mortality. Second, nutrition-
al status was documented by BMI, while it might have been
valuable to relate dietary composition and physical activity
with the level of handgrip strength as well as its predictive
value of mortality, but these determinants were not formally
documented. Lastly, because diseases were not registered, the
possible effects of diseases on handgrip strength could not be
studied and neither could handgrip strength be assessed as a
predictor of morbidity.
In conclusion, this study shows that handgrip strength
declines over age with a similar rate and functions equally
well as an independent predictor of mortality in a traditional
rural African population compared with western populations.
Across divergent environments, in different populations, and
despite variations in lifestyle, handgrip strength can be easily
and universally used to identify frail people at increased risk
of mortality.
Key points
•Handgrip strength in rural Africa is lower than in western
populations due to a lower height and BMI.
•Handgrip strength declines similarly over age in rural Africa
and western populations.
•Handgrip strength is an independent predictor of mortality
in rural Africa.
•Handgrip strength can be used as a universal marker of
ageing.
Acknowledgements
The authors are grateful for the dedicated assistance of the
local staff of the research team in the Garu-Tempane
District in Ghana. The authors are grateful for the help of
Dr U.K. Eriksson and H. Sanchez-Faddiev in the field
work and of Z. Li in the analyses and the drafting of the
manuscript.
Conflicts of interest
None declared.
Funding
The research in the Ghanaian research area was supported by
the Netherlands Foundation for the Advancements of Tropical
Research [WOTRO 93-467]; the Netherlands Organization
for Scientific Research [NWO 051-14-050]; the European
Union-funded Network of Excellence LifeSpan [FP6
036894]; a grant of the Board of Leiden University Medical
Center; and Stichting Dioraphte. The measurement of hand-
grip strength in the Leiden Longevity Study was supported
by the Netherlands Genomics Initiative/the Netherlands
Organization for Scientific Research [NGI/NWO 05040202,
NCHA 050-060-810] and the European Union-funded
project MYOAGE [HEALTH-2007-2.4.5-10]. The sponsors
had no role in the study design, subject recruitment, data col-
lection and analysis, decision to publish or preparation of the
manuscript.
Authors’contributions
Study concept and design: J.J.E.K., D.v.B. and R.G.J.W.
Recruitment of subjects and execution of the measurements:
J.J.E.K. and D.v.B. Provision of data from the Leiden Longevity
Study: D.v.H. Statistical analyses: J.J.E.K. Interpretation of
the results: all authors. Drafting of the manuscript: J.J.E.K.
Intellectual contribution to and critical revision of the manu-
script: D.v.B., D.v.H. and R.G.J.W.
Supplementary data
Supplementary data mentioned in the text are available to
subscribers in Age and Ageing online.
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