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Positive Association between Altitude and Suicide in 2584 U.S. Counties

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Brenner, Barry, David Cheng, Sunday Clark, and Carlos A. Camargo, Jr. Positive association between altitude and suicide in 2584 U.S.counties. High Alt. Med. Biol. 12: 31-35 2011.-Suicide is an important public health problem worldwide. Recent preliminary studies have reported a positive correlation between mean altitude and the suicide rate of the 48 contiguous U.S.states. Because intrastate altitude may have large variation, we examined all 2584 U.S. counties to evaluate whether an independent relationship between altitude and suicide exists. We hypothesized that counties at higher elevation would have higher suicide rates. This retrospective study examines 20 yr of county-specific mortality data from 1979 to 1998. County altitude was obtained from the U.S. Geologic Survey. Statistical analysis included Pearson correlation, t tests, and multivariable linear and logistic regression. Although there was a negative correlation between county altitude and all-cause mortality (r = -0.31, p < 0.001), there was a strong positive correlation between altitude and suicide rate (r = 0.50, p < 0.001). Mean altitude differed in the 50 counties, with the highest suicide rates compared to those with the lowest rates (4684 vs. 582 ft, p < 0.001). Controlling for percent of age >50 yr, percent male, percent white, median household income, and population density of each county, the higher-altitude counties had significantly higher suicide rates than the lower-altitude counties. Similar findings were observed for both firearm-related suicides (59% of suicides) and nonfirearm-related suicides. We conclude that altitude may be a novel risk factor for suicide in the contiguous United States.
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Scientific Article
Positive Association between Altitude
and Suicide in 2584 U.S. Counties
Barry Brenner,
1
David Cheng,
1
Sunday Clark,
2
and Carlos A. Camargo, Jr.
3
Abstract
Brenner, Barry, David Cheng, Sunday Clark, and Carlos A. Camargo, Jr. Positive association between altitude
and suicide in 2584 U.S.counties. High Alt. Med. Biol. 12, 2011— Suicide is an important public health problem
worldwide. Recent preliminary studies have reported a positive correlation between mean altitude and the
suicide rate of the 48 contiguous U.S.states. Because intrastate altitude may have large variation, we examined all
2584 U.S. counties to evaluate whether an independent relationship between altitude and suicide exists. We
hypothesized that counties at higher elevation would have higher suicide rates. This retrospective study ex-
amines 20 yr of county-specific mortality data from 1979 to 1998. County altitude was obtained from the U.S.
Geologic Survey. Statistical analysis included Pearson correlation, ttests, and multivariable linear and logistic
regression. Although there was a negative correlation between county altitude and all-cause mortality (r¼0.31,
p<0.001), there was a strong positive correlation between altitude and suicide rate (r¼0.50, p<0.001). Mean
altitude differed in the 50 counties, with the highest suicide rates compared to those with the lowest rates (4684
vs. 582 ft, p<0.001). Controlling for percent of age >50 yr, percent male, percent white, median household
income, and population density of each county, the higher-altitude counties had significantly higher suicide
rates than the lower-altitude counties. Similar findings were observed for both firearm-related suicides (59% of
suicides) and nonfirearm-related suicides. We conclude that altitude may be a novel risk factor for suicide in the
contiguous United States.
Key Words: altitude; suicide; firearm; obesity; hypoxia
Introduction
In2002 there were at least 1.5 million deaths world-
wide from self-inflicted injuries, which made it the 14th
most common cause of death (Mathers and Loncar, 2006). In
the next 20 yr, suicide is expected to reach over 2 million
deaths and will rank 12th in the world as a cause of mortality
(Mathers and Loncar, 2006). Recognized risk factors for sui-
cide include older ages, male sex, white race, low income,
owning firearms, isolation, divorce, serotonin dysfunction,
incarceration, substance abuse, and reduced levels of choles-
terol (Stack, 2000; Ellison and Morrison, 2001; Goldsmith,
2001; Hemenway and Miller, 2002; Singh and Siahpush, 2002;
Zill et al., 2004; Dumais et al., 2005; Daly et al., 2007). Psy-
chiatric illness, mood disorders, and sociocultural issues are
also important risk factors (Nock, 2010). Alcoholism has been
associated with high suicide rates in Euopean countries, and
impulsiveness and political violence are associated with sui-
cide in southeast Asian countries (Maris, 2001). For unex-
plained reasons, suicide rates are higher in the western United
States (CDC, 1997).
Increased altitude has recently been shown to have a pro-
tective association with certain medical illnesses, with ap-
parent decreases in mortality among patients with end-stage
renal disease receiving dialysis (Winkelmayer et al., 2009),
coronary artery disease (Baibas et al., 2005; Faeh et al., 2009),
and stroke (Faeh et al., 2009). By contrast, increased altitude
may enhance psychiatric disorders, such as panic attacks
(Roth et al., 2002). We (Cheng et al., 2005) have hypothesized a
positive correlation between the mean altitude and suicide
rate of the 48 contiguous United States. Because intrastate
altitude may have wide variations, we have examined all
2584 contiguous U.S. counties to evaluate whether an inde-
pendent relationship between altitude and suicide exists. We
1
Department of Emergency Medicine, University Hospitals Case Medical Center, Cleveland, Ohio.
2
Division of General Internal Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
3
Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts.
HIGH ALTITUDE MEDICINE & BIOLOGY
Volume 12, Number 1, 2011
ªMary Ann Liebert, Inc.
DOI: 10.1089/ham.2010.1058
1
hypothesized that counties at high elevation would have
higher suicide rates.
Methods
This retrospective study used mortality data assembled by
the U.S. Centers for Disease Control and Prevention (CDC).
The CDC mortality data are based on the underlying cause of
death, which is defined by the World Health Organization as
‘‘the disease or injury which initiated the train of events
leading directly to death, or the circumstances of the accident
or violence which produced the fatal injury.’’ (CDC Suicide
Mortality, 2009). Suicide was selected by CDC staff from the
conditions entered by the physician on the cause of death
section of the original death certificate. When more than one
cause or condition was entered by the physician, the under-
lying cause was determined by the sequence of conditions on
the certificate, provisions of the International Classification of
Diseases (ICD), and associated selection rules and modifica-
tions. For analysis of injury mortality data, the causes of death
were classified by both intent and mechanism. The focus of
the present study was death from self-inflicted injury, and the
mechanism was either firearm-related or nonfirearm-related.
Accordingly, we used the Ninth International Classifica-
tion of Disease (ICD9) codes to identify suicide deaths (ICD9
codes 950–959) and deaths from any cause (ICD9 codes 000–
999.9). The suicide rates reported are age-adjusted deaths
(>5 yr), with deaths per 100,000 at the county level for the
contiguous 48 states during the 20-yr span of ICD 9 classifi-
cation from1979 to 1998. Counties with unreliable suicide
rates were defined by the CDC as having 20 cumulative
deaths during this 20-year interval. All counties with unreli-
able data (n¼484 of 3068; 15.8%) were excluded from the
primary analysis.
Covariates include percentage of people of age >50 yr,
male, white, and median household income and population
density, with all these variables obtained from the 1990 U.S.
Census (U.S. Population Census, 2009). The 1990 Census was
chosen, since this was midway in the 20-yr period that we
used to extract mortality data from the CDC.
County elevation for all 2584 counties was obtained from
the U.S. Geologic Survey (U.S. Geological County Survey,
2009). The latitude and longitude coordinates of the center of
each U.S. county were joined to the National Elevation Da-
tabase (NED) to determine and represent the elevation for
each county. NED is a seamless database composed of the best
raster elevation data only for the 48 contiguous U.S. states;
NED’s vertical accuracy is reported as 8 ft (root mean square
error) (National Elevation Database, 2009).
Statistical analysis was performed using Stata 10.0 from
StataCorp in College Station, Texas, USA. The specific tests
were Pearson correlation, Student’s ttest, and multivariable
linear and logistic regression. In addition to the primary anal-
ysis on altitude and suicide mortality, we examined altitude
and all-cause mortality. We also performed a sensitivity anal-
ysis to examine if the altitude–suicide finding was modified by
the firearm status (yes or no) of the suicide death. All pvalues
are two-tailed, with p<0.01 considered statistically significant.
Results
During the 1979–1998 span, there were 596,704 (1.4%)
suicide deaths in the United States, among 42,868,100 total
deaths. Overall, the median age-adjusted suicide rate per
100,000 in a U.S. county was 14 (interquartile range [IQR], 12–
17). The median suicide rate across counties was higher
among men (24, IQR 21–29) than women (6, IQR 5–7). When
only the suicide rate by firearms was considered, the median
rate was 10 per 100,000 (IQR, 8–12), while the nonfirearm
median rate was 4 (IQR 3–5).
With regard to primary exposure, county elevation, the
overall median value across counties was 892 ft (IQR 463–
1594 ft). With regard to covariates, the median of the
percentage of counties that was of age >50 yr was 27% (IQR
24–31%). The median value for other factors was male 49%
(IQR 48–50%), white 94% (IQR 81–98%), median family
income $22,662 (IQR $19,623–$26,802), and population
density 38 (IQR 16–90) individuals per square mile.
Despite a negative correlation (r¼0.31, p<0.001) be-
tween county altitude and the all-cause mortality rate, there
was a strong positive correlation (r¼0.50, p<0.001) between
altitude and suicide rate at the county level (Fig. 1). Positive
correlations were also observed for both firearm-related sui-
cides (r¼0.40, p<0.001) and nonfirearm-related suicides
(r¼0.31, p<0.001). Controlling for five potential confounders
(percent of age >50 yr, percent male, percent white, median
household income, median family income, and population
density of each county), increasing altitude deciles were as-
sociated with significantly higher suicide rates (Table 1). The
threshold value for increased suicide rates occurred in the
range of 2000–2999 ft (Table 1). Similar findings were ob-
served for firearm-related suicides, which comprise 59%
(352,052 firearm suicides per 596,704 total suicides) of all
suicides (Table 1).
We then compared the 50 counties with the highest suicide
rates against the 50 counties with the lowest suicide rates in
the United States. The ratio in average suicide rates between
the 50 highest and lowest counties was 4.2 (30.5:7.2). Mean
altitude greatly differed between the 50 counties with the
highest suicide rates compared with those with the lowest
rates (4684 vs. 582 ft, p<0.001).
Because the Mountain Region (CDC region 8) is already
known to have high suicide rates (CDC, 1997), we repeated
this analysis, after removing the CDC Mountain Region, and
then determined the 50 counties with the highest suicide rates
and the 50 counties with the lowest suicide rates in the United
States. The ratio between suicide rates remained high
(25.5:7.3 ¼3.5). Without the Mountain Region, mean altitude
differed between the 50 counties with the highest suicide rates
compared with those with the lowest rates, respectively (2075
vs. 497 ft, p<0.001).
Because 59% of suicides involve firearms, we restricted the
analysis to suicide by firearms only. We then compared the 50
counties with the highest firearm suicide rates with the 50
counties with the lowest firearm suicide rates. The ratio of the
suicide rates in these two groups of counties also was elevated
(22.6:2.9 ¼7.8). The mean altitude again differed between the
50 counties with the highest firearm suicide rates compared
with those with the lowest firearm suicide rates (4098 vs.
324 ft, p<0.001).
It could be argued that altitude-related suicide may be
owing to more firearm usage at higher altitude, and suicide
per se may be unrelated to altitude. However, we also found a
positive relationship between altitude and nonfirearm-related
suicide. There was a 12.5-fold (10.0:0.8) difference in suicide
rate between the counties with the 50 highest nonfirearm
suicides versus those with the lowest nonfirearm suicides,
2 BRENNER ET AL.
and the mean altitude in the 50 counties with the highest and
lowest nonfirearm suicide rates was 3699 ft versus 954 ft
(p<0.001).
All the results in the previous analyses have been calcu-
lated using the reliable suicide data from 2584 counties. As
noted under Methods, 484 counties did not have reliable data
available owing to their having 20 suicide deaths in a 20-yr
span; consequently, they were excluded from our analyses.
Perchance, these missing data would affect the association
between altitude and suicide. When these unreliable suicide
rates were used, in lieu of removing them from the analysis,
the positive correlation between county elevation and suicide
rate persisted (r¼0.45, p<0.001).
Discussion
Using U.S. national data from 1978 to 1998, we found that
county altitude had a significant positive association with
overall suicide rates, firearm-related suicide rates, and
nonfirearm-related suicides. Altitude was associated with
overall suicide rate even after controlling for five potential
confounders. The correlation between altitude and suicide
could be mitigated by a positive correlation between altitude
and all-cause mortality over the same period. On the contrary,
we found a significant negative correlation between altitude
and all-cause mortality, a finding that highlights the novelty
and strength of the observed relationship between altitude
and suicide. Using a different methodology, a similar, strong
positive correlation between altitude and suicide rates has
recently been reported by Kim and colleagues, (2011) using all
counties in the United States as well as all 233 counties in
South Korea.
Our previous abstract work on altitude and suicide (Cheng
et al., 2005) was done by comparing mean state altitude with
suicide data for entire states and was repeated by others us-
ing peak altitude for each state and state capital city eleva-
tions (Haws et al., 2009). Although both studies reported
strong correlations (r¼0.75 and 0.74, respectively), they were
Table 1. Adjusted Association between County Elevation and Suicide Rate (per 100,000)
in 2584 United States Counties
a
Overall suicide rate Firearm suicide rate Nonfirearm suicide rate
County elevation (ft) nb95% CI b95% CI b95% CI
<1000 1743 Reference Reference Reference
1000–1999 722 0.17 0.17, 0.50 0.15 0.47, 0.16 0.36 0.19, 0.53
2000–2999 230 3.25 2.64, 3.86 2.05 1.47, 2.62 1.01 0.69, 1.32
3000–3999 116 3.38 2.56, 4.20 2.42 1.67, 3.17 1.18 0.76, 1.59
4000–4999 98 6.23 5.45, 7.02 4.76 4.03, 5.49 1.94 1.53, 2.34
5000–5999 55 9.60 8.56, 10.63 6.26 5.30, 7.22 2.92 2.39, 3.45
6000–6999 41 7.95 6.77, 9.13 5.91 4.83, 7.00 1.85 1.26, 2.45
7000–7999 28 8.47 7.01, 9.91 6.11 4.79, 7.43 2.29 1.57, 3.01
8000–8999 16 7.40 5.40, 9.40 6.00 4.17, 7.80 0.60 0.39, 1.60
9000 18 9.12 7.20, 11.050 6.69 4.78, 8.61 2.57 1.52, 3.62
CI, confidence interval.
a
Controlling for percent of age >50 yr, percent male, percent white, median household income, median family income, and population
density of each county.
0
500
1000
1500
2000
2500
3000
3500
4000
4500
4.2 - 9.3
9.4 - 10.3
10.4 - 10.9
11.0 - 11.5
11.6 - 11.9
12.0 - 12.4
12.5 - 12.7
12.8 - 13.1
13.2 - 13.5
13.6 - 13.9
14.0 - 14.4
14.5 - 14.8
14.9 - 15.3
15.4 - 15.8
15.9 - 16.5
16.6 - 17.3
17.4 - 18.2
18.3 - 19.5
19.6 - 22.0
22.1 - 49.4
County specific suicide rates (per 100,000)
Median Elevation (Feet)
FIG. 1. Suicide rate by vingtiles of U.S. county altitude.
U.S. SUICIDE RATES INCREASE WITH ALTITUDE 3
inconclusive. In these studies the mean or highest state alti-
tude (Cheng et al., 2005; Haws et al., 2009) or the elevation of
the state capital city (Haws et al., 2009) was used to represent
the altitude of the entire state. However, because U.S. states
vary greatly in altitude and the foregoing methodology se-
verely minimizes this variation, we considered these initial
findings to be of a preliminary nature only. For example, New
York varies from sea level to 5344 ft and California from 282
to 14,505 ft. With such heterogeneity in elevation on a state
basis, it would be difficult to conclude that elevation might be
related to suicide, despite the strong ecologic correlation.
Counties vary much less in altitude than an entire state. For
this reason, we thought that reexamining this association on a
county level would address this limitation.
If there were no link between altitude and suicide, there is
little reason why the 50 counties with the highest suicide rates
should differ in elevation when compared to the counties with
the 50 lowest suicide rates. We found, however, that there was
an almost 8-fold difference in altitude in these two groups of
counties. When suicides were divided by firearm status (yes
or no), the difference in altitude between the 50 counties with
the highest and lowest suicide rates was 4.3 and 3.8, respec-
tively. Prior reports of increased suicides in the U.S. Mountain
Region (e.g., Colorado) have prompted speculation that the
excess is owing to greater access to firearms, increased isola-
tion, or reduced income (CDC, 1997). Even after controlling
for these variables in our analysis, the positive correlation
between altitude and suicide still exists, which suggests that
the increased suicide rate in the regions with greatest altitude,
such as the Mountain Region, may be owing to, at least in
part, its altitude per se.
Although a discussion of potential mechanisms is specu-
lative at this juncture, we believe it appropriate to guide fur-
ther investigation into this novel finding. For example,
altitude is a well-known cause of hypoxia, and the greater the
elevation, the greater the hypoxia. Chronic hypoxia also is
thought to increase mood disturbances, especially in patients
with emotional instability (Shukitt and Banderet, 1988; Ni-
cholas et al., 2000; Nock et al., 2010). The relationship between
mood and hypoxia is complex, because oxygen therapy, while
beneficial to pulmonary function in hypoxic patients with
sleep apnea, was found not to improve mood (Yu et al., 1999).
Humans have well-known physiologic responses to mild
and moderate chronic hypoxia, such as increased 2,3-
diphosphoglycerate and a shift to the right in the hemoglobin–
oxygen dissociation curve (Winslow, 2007); but not all
people respond equally to hypoxia or increased altitude
owing to variations in hemoglobin affinity for oxygen and
other mechanisms (Winslow, 2007). If the mechanism of the
suicide–altitude relationship were hypoxia, we would antic-
ipate that there may be increased mood disturbances at high
altitude in those with sleep apnea (Peppard et al., 2009) or
moderate or heavy smokers at high altitude.
Future studies may or may not confirm the altitude–suicide
association in other parts of the world. Should the association
not be present in some other locations with comparable var-
iation in altitude, it is possible that our findings are owing to
conditions that are more common in the United States. For
example, although obesity rates are rising worldwide, they
have been high in the United States for decades (Peppard et
al., 2009). Obesity is known to cause increased hypoxia owing
to sleep apnea and thereby may create a mood disturbance
(Rigby et al., 2004); one might anticipate that the altitude–
suicide finding might be heightened in obese individuals.
Known periodic breathing at high altitude may further ex-
acerbate the effects of sleep apnea and nocturnal hypoxia
(West et al., 1986, Khoo et al., 1996; Bloch, 2010).
A potential limitation regarding the altitude–suicide find-
ing is heterogeneity in altitude within counties. Although the
problem is obviously worse when considering entire states
(Cheng et al., 2005), it is a lesser concern even for large
counties. However, the consistency of the association across
different measures of altitude [i.e., when measured at both the
state level (Cheng et al., 2005; Haws et al., 2009) and now the
county level] suggests that the association is not spurious. We
addressed other potential limitations in the analysis (e.g.,
contribution of Mountain states, exclusion of unreliable data),
and the altitude–suicide finding was very robust.
Despite the strong association between suicide and alti-
tude, other factors may be responsible for this association that
are directly related to high altitude per se, for example, low
barometric pressure (Shukitt et al., 1998). Many demographic,
psychiatric, and sociocultural factors are associated with
suicide, and association between high altitude and suicide is
speculative. But when other risk factors were considered, the
strong association between altitude and suicide was still
present in suicides overall and in suicides both with and
without firearms. This strong association (r¼0.50) is rendered
even stronger by the overall negative association between all
deaths and altitude (r¼0.31).
In summary, altitude is strongly associated with suicide
rates in the United States. This novel finding is not explained
by county differences in demographic factors, income, or
geographic isolation. Future studies might focus on the indi-
vidual differences between these high and low altitude areas,
both at the biochemical level (e.g., glycolysis, serotonin me-
tabolism, oxygen transport) and the level of the entire or-
ganism (e.g., differences in arterial oxygen compared with
pulse oximetry, body mass index, sleep apnea, smoking, or
behavioral distinctions). Ultimately, this mechanistic search
might help clinicians to identify individuals at high altitude
who may be amenable to relocation to lower altitude areas,
oxygen therapy, or special monitoring and intervention (U.S.
Department of Health and Human Services, 2009).
Acknowledgments
Dr. Camargo was supported in part by NIH U01 MH-88278
(Bethesda, Maryland, USA). The authors would like to thank
Mr. Lazar Muller for his help with the data collection and
entry.
Disclosures
The authors have no conflicts of interest or financial ties to
disclose.
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Address all correspondence to:
Barry E. Brenner, MD, PhD
Department of Emergency Medicine
University Hospitals Case Medical Center
11100 Euclid Avenue
Cleveland, OH 44106
E-mail: barry.brenner@uhhospitals.org
U.S. SUICIDE RATES INCREASE WITH ALTITUDE 5
... Both MDD and TRD are linked to suicidal ideation and suicidal behavior. Rates of MDD and suicide both increase with altitude of residence [4][5][6][7][8][9][10][11][12][13][14], and people at altitude are exposed to hypobaric hypoxia (low partial pressure of oxygen). A similar pattern of increased rates of MDD and suicide is seen in people exposed to chronic hypoxia via disorders such as asthma, chronic obstructive pulmonary disorder (COPD), chronic bronchitis, cardiovascular disease and smoking [15][16][17][18][19][20]. ...
... The hypobaric hypoxia experienced with living at altitude can cause deficits in blood oxygen levels and brain bioenergetic markers at as moderate an altitude as 4500 ft [23,25]. Living at altitude is linked to higher risk for MDD [4][5][6][7], and suicide [8][9][10][11][12][13][14] as well as for abuse of methamphetamine, cocaine and prescription opioids [72][73][74]. Both MDD and substance use disorders are linked to brain hypometabolic function and use of energetic compounds such as CRMH has been recommended as treatment for these metabolic disorders [33,34]. ...
Article
Full-text available
Background: Rates of major depressive disorder (MDD) increase with living at altitude. In our model, rats housed at moderate altitude (in hypobaric hypoxia) exhibit increased depression-like behavior, altered brain serotonin and a lack of antidepressant response to most selective serotonin reuptake inhibitors (SSRIs). A forebrain deficit in the bioenergetic marker creatine is noted in people living at altitude or with MDD. Methods: Rats housed at 4500 ft were given dietary creatine monohydrate (CRMH, 4% w/w, 5 weeks) vs. un-supplemented diet, and impact on depression-like behavior, brain bioenergetics, serotonin and SSRI efficacy assessed. Results: CRMH significantly improved brain creatine in a sex-based manner. At altitude, CRMH increased serotonin levels in the female prefrontal cortex and striatum but reduced male striatal and hippocampal serotonin. Dietary CRMH was antidepressant in the forced swim test and anti-anhedonic in the sucrose preference test in only females at altitude, with motor behavior unchanged. CRMH improved fluoxetine efficacy (20 mg/kg) in only males at altitude: CRMH + SSRI significantly improved male striatal creatine and serotonin vs. CRMH alone. Conclusions: Dietary CRMH exhibits sex-based efficacy in resolving altitude-related deficits in brain biomarkers, depression-like behavior and SSRI efficacy, and may be effective clinically for SSRI-resistant depression at altitude. This is the first study to link CRMH treatment to improving brain serotonin.
... Depression and suicide rates are intimately linked (Möller, 2003) and have both been associated with living at altitude; this has been reported for depression (DelMastro et al., 2011;Gamboa et al., 2011;Wang et al., 2019;Zaeh et al., 2016) and suicide (Alameda-Palacios et al., 2015;Betz et al., 2011;Bezerra Filho et al., 2012;Brenner et al., 2011;Haws et al., 2009;Kim et al., 2011). Already moderate altitudes of about 600 -900 m may affect both depression and suicide rates Kious et al., 2019;Sabic et al., 2019). ...
Article
Adequate oxygen supply is essential for the human brain to meet its high energy demands. Therefore, elaborate molecular and systemic mechanism are in place to enable adaptation to low oxygen availability. Anxiety and depressive disorders are characterized by alterations in brain oxygen metabolism and of its components, such as mitochondria or hypoxia inducible factor (HIF)-pathways. Conversely, sensitivity and tolerance to hypoxia may depend on parameters of mental stress and the severity of anxiety and depressive disorders. Here we discuss relevant mechanisms of adaptations to hypoxia, as well as their involvement in mental stress and the etiopathogenesis of anxiety and depressive disorders. We suggest that mechanisms of adaptations to hypoxia (including metabolic responses, inflammation, and the activation of chemosensitive brain regions) modulate and are modulated by stress-related pathways and associated psychiatric diseases. While severe chronic hypoxia or dysfunctional hypoxia adaptations can contribute to the pathogenesis of anxiety and depressive disorders, harnessing controlled responses to hypoxia to increase cellular and psychological resilience emerges as a novel treatment strategy for these diseases.
... Several bioclimatic factors, including sunlight, temperature, humidity, and altitude, have been associated with the seasonality of suicides. [27][28][29] In particular, researchers have suggested that the abrupt circadian phase-shifting caused by the increased light exposure in spring is a plausible underlying mechanism of the spring surge of suicide. 10,11 According to the circadian rhythm model, the misalignment between the endogenous and environmental circadian rhythms could lead to mood dysregulation in susceptible individuals, consequently contributing to the spring surge of suicide and mania. ...
Article
Objective: This study aimed to investigate the changing seasonal pattern of suicides in Korea between 2000 and 2019. Methods: We calculated a seasonal pattern of suicides between 2000 and 2019 using a non-stationary cosinor model. In addition, we estimated the effect of each month on the suicide incidence compared to a reference month, using a generalized linear model with a categorical variable of the month. Then, we visualized the rate ratio curves of suicides by gender, age group, and subperiod. Results: We observed a seasonal pattern of suicides in Korea with a spring peak and a winter trough. The seasonal ups and downs were most pronounced in suicides among the elderly ≥65 years. However, the seasonal pattern has not been consistent over the past two decades, with lowering seasonal peaks since 2012. The amplitude of seasonality was also lower in 2010-2019 than in 2000-2009. Conclusion: The seasonal pattern of suicides seems to have diminished in Korea in recent years. Thus, we need further studies to investigate climatic and non-climatic factors influencing the seasonality of suicides and the consequence of the change.
... The effects of altitude on mood are evidenced from another point of view from multiple studies that have found higher rates of suicide in residents of altitude; however, these are studies were developed from a database with limitations (Brenner et al., 2011;Reno et al., 2018). Betz et al. (2011) conducted an individual analysis of cases; it found that individuals who suffered suicide were more likely to have relatives with a history of depression; in the same way, several factors such as age, gender, and residence can influence access to health care in high-altitude populations. ...
Article
Ortiz-Prado, Esteban, Katherine Simbaña-Rivera, Diego Duta, Israel Ochoa, Juan S. Izquierdo-Condoy, Eduardo Vasconez, Kathia Carrasco, Manuel Calvopiña, Ginés Viscor, and Clara Paz. Optimism and health self-perception-related differences in indigenous Kiwchas of Ecuador at low and high altitude: a cross-sectional analysis. High Alt Med Biol 00:000-000, 2021. Background: Living at high altitude causes adaptive responses at every physiological and molecular level within the human body. Emotional and psychological short- or long-term consequences, including mood changes, higher mental overload, and depression prevalence, as well as increased risk to commit suicide have been reported among highlanders. The objective of this report is to explore the differences in self-reported dispositional optimism and health perception among sex-, age-, and genotype-controlled indigenous Kiwcha natives living at two different altitudes. Methods: A cross-sectional analysis of the comparison of means of subscales and summary scores of the 36-item short-form health survey (SF-36) self-reported questionnaire and the Life Orientation Test-Revised was conducted among 219 adults Kiwchas living at low (230 m) and high altitude (3,800 m) in Ecuador. Results: High-altitude dwellers presented lower scores in all the studied dimensions of SF-36 and the total score. Differences were found for the role limitation sphere due to vitality (p = 0.005), mental health (p = 0.002), and social functioning (p = 0.005). In all the cases, participants living at low altitudes scored higher than those living at high altitudes. Lowland women were more optimistic than their high-altitude counterparts. Conclusions: We observe that populations located at high altitudes have more unfavorable self-reported health states. Although our results depict the existence of significant differences in the health status of indigenous peoples living at different altitudes, further studies are needed to explain in depth the sociodemographic and/or environmental factors that might underlie these differences.
... We included a group of covariates, representing demographic, socioeconomic and exposure to health risk factors, based on previous studies (Brenner et al., 2011;Kious et al., 2018;Risal et al., 2016). Among the demographic covariates we included sex (male or female), age in years (18-29, 30-59 or 60 years or older), marital status (single, cohabiting or married, separated, divorced or widowed), educational level (no formal schooling, primary level, secondary level or higher education) and area of residence (urban or rural). ...
Article
Background In high altitude regions, people experience biological, inflammatory and brain structure changes that increase the risk of depressive symptoms. The aim of this study was to determine the association between altitude and depressive symptoms in the Peruvian population, adjusting by demographic, socioeconomic and exposure to health risk factors. Methods We performed a cross-sectional analytical study of data collected annually by the Demographic and Family Health Survey during the period 2013-2020. The presence of depressive symptoms during the last 14 days prior to the survey were measured using scores obtained from the Patient Health Questionnaire (PHQ-9). A generalized linear model (GLM) of gamma family and log link function was used to report the crude and adjusted β coefficients. A quantile regression model was performed as a sensitivity analysis. Results Data from a total of 215,409 participants were included. After adjusting for demographic, socioeconomic and health risk exposures, the GLM showed that an increase in every 100 meters of altitude of residence was positively and significantly associated with the depressive symptoms score (β=0•01 [95% confidence interval: 0•01-0•01]). Limitations The length of residence in high altitude areas of the population included cannot be established, requiring future research to determine if the results of the present study are similar in native people or permanent residents of high altitude regions. Conclusions Altitude was positively associated with depressive symptom scores. Our results will allow the development of mental health interventions based on factors that increase the likelihood of depressive symptoms in high-altitudes.
... These factors were shown to be associated with MDD, i.e., exposure to traffic-related air pollution evoked depressive symptoms in children (50), and other studies confirmed the association between air pollution and a higher risk for suicide and anxiety (51,52). Similarly, a positive association between altitude and suicidal risk was observed (53). Another study reported that students moving from a low altitude to a high altitude (above 900 m) developed more depressive and anxiety symptoms compared to a control group that remained at low altitude (54). ...
Preprint
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Major depressive disorder (MDD) causes enormous individual suffering and socioeconomic costs. Biochemical mechanisms leading to MDD are poorly understood and therapy success is not satisfactory. At present, there is evidence of low-grade inflammation, oxidative stress, and most interestingly, a disturbed energy metabolism in MDD and other mental health diseases. Mitochondria play a central part in energy production and stress signaling. Mitochondrial electron transport chain uses molecular oxygen (O2) as final electron acceptor during adenosine triphosphate production attributing a crucial role to an intact O2 supply. Adaptation to altered O2 availability by the highly conserved hypoxic response is essential for maintaining allostasis. Previous research confirmed the role of O2 metabolism in the pathophysiology of MDD. In this perspective article, we compile the evidence linking O2 transport, O2 homeostasis, and mitochondrial energy metabolism to MDD. Furthermore, we hypothesize that inflammation and oxidative stress-related alterations in O2 transport might lead to a hypoxic response, which explains changes in O2 homeostasis and energy metabolism in MDD. Our forthcoming studies will investigate the interplay between energy metabolism and O2 homeostasis in MDD that aim to improve the overall understanding of the pathophysiology of MDD and to guide medical and psychological diagnostics towards a holistic strategy.
Article
Suicide is a major public health problem affecting US Veterans and the US in general. Many variables (e.g., demographic, clinical, biological, geographic) have been associated with risk for suicide and suicidal behavior, including altitude; however, the exact nature of the relationship between altitude and suicide remains unclear in part due to the fact that previous studies have used either geospatial data or individual-level data, but not both. Prior research has also failed to consider the full range of suicidal thoughts and behaviors, ranging from suicidal ideation to suicide deaths. Accordingly, the objective of the present research was to use both geospatial data (county and zip codes) and individual-level data to comprehensively assess the association between altitude and suicide mortality, suicide attempts, and suicidal ideation among US Veterans between 2000 and 2018. Taken together, our results demonstrate that there is a strong correlation between altitude and suicide rates at all the levels investigated and using different statistical analyses and even after controlling for significant covariates such as percent of age >50yr, percent male, percent white, percent non-Hispanic, median household income, and population density. We show that there is a positive correlation between altitude and suicide attempts especially when controlling by the covariates and a weak correlation between altitude and suicide ideation and the combination of suicide, suicide attempts and suicide ideation.
Article
Objective: The purpose of this systematic review was to synthesize the existing global literature examining the relationship between altitude and suicide. Method: Using the electronic databases PubMed, CINAHL, EMBASE, and PsychInofo published articles in English that addressed the relationship between altitude and suicide as a primary or secondary aim, and included human subjects, where identified. Studies were assessed for quality based on methodological approach and data relevance on a three-point scale (strong, moderate, or weak). Results: Of the 19 studies related to the purpose and aims, 17 reported evidence of a positive correlation between altitude and increased suicide. Vast design differences were employed within the literature, individual-level suicide data was identified as the preferred level of analysis. Discussion: The relationship between altitude and suicide is an evolving science with a small but growing body of literature suggesting altitude is associated with an increased risk of suicide. This review identifies the need for additional studies examining both individual-level suicide data and improving geographic precision. Public health nurses have a responsibility to carefully examine the quality of studies and the strength of the evidence when addressing variables associated with suicide.
Conference Paper
Over the last decade, Oil & Gas operations have come under tremendous pressures due to increasing production demands and venturing into harsher environmental conditions, increasing the health risks to crew with underlying medical conditions. Although there are strict medical fitness, requirements in place to reduce the vulnerability of crewmembers, increasing number Non Accidental Deaths (NAD) have challenged the Oil & Gas operations. NAD risks are often linked with medical assessment/fitness to work, training and medical emergency response, NAD questions the adequacy of management controls at work locations, especially in remote locations. ADNOC Group Companies adopt very HSE high standards to protect the workers, environment and assets; however, the risks of aggravating underlying medical conditions, illnesses or disorders often materialize and result in NADs. An extended analysis of over historical NAD events was performed and strengths of NAD barriers (Tayab et al, 2012) was assessed. Based on the review NAD Barriers were further redefined as follow:Adequacy of pre-employment medical assessmentAlert of underlying medical conditionsFollow up on chronic medical conditionsAlert for abnormal behavioursAwareness & Training It was found that over 70% of NAD cases were triggered due to aggravation of chronic illnesses, approximately 50 % of NAD cases were triggered during the first year of employment, 77% of NAD cases were due to cardiovascular illnesses and 18% were due to suicides and 13% were attributed to COVID & other factors. Additional NAD barriers were identified to update the barrier analysis as follows:Alert for abnormal behaviorReadiness to manage Medical EmergenciesWelfare & Counselling
Article
Objective: Rural locations have been associated with suicidal risk; low population density may be a relevant factor. Accordingly, we investigated hypothesized associations between suicidal ideation and behavior with selected geographic and population-related measures and other factors. Methods: Consenting adult patients at a mood disorder center in Cagliari, Sardinia, were assessed for the presence of suicidal ideation and acts and their association with selected demographic and clinical factors as well as indicators of urbanicity and rurality, including distance from the region's main metropolitan area, population density, altitude, and population growth trends. Results: Of 5,668 subjects, 27% had an indication of lifetime suicidal behavior or ideation; 8.6% had at least one suicidal act. Low population density, higher altitude and their interaction, distance from the metropolitan center of the main city (Cagliari), and population decline were associated with greater risk of suicidal ideation or behavior. In addition, and as expected, alcohol or substance abuse, diagnosis of mood disorders, higher depression ratings at intake, being younger at illness-onset, family history of suicide or other psychiatric disorder, being female, unmarried, separated or divorced, currently smoking cigarettes, being unemployed, and having experienced sexual abuse all were more likely in subjects with suicidal ideation or behavior. Conclusion: Suicidal ideation and behavior were associated with indicators of social isolation as well as with previously reported clinical and demographic risk factors.
Article
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Mental disorders are among the strongest predictors of suicide attempts. However, little is known regarding which disorders that are uniquely associated with suicidal behavior because of high levels of psychiatric comorbidity. We examined the unique associations between individual disorders and subsequent suicidal behavior (suicide ideation, plans and attempts) using data from the National Comorbidity Survey Replication, a nationally representative household survey of 9282 US adults. Results revealed that approximately 80% of suicide attempters in the United States have a temporally prior mental disorder. Anxiety, mood, impulse-control and substance use disorders all significantly predict subsequent suicide attempts in bivariate analyses (odds ratios (OR)=2.7–6.7); however, these associations decrease substantially in multivariate analyses controlling for comorbidity (OR=1.5–2.3) but remain statistically significant in most cases. Disaggregation of the observed effects reveals that depression predicts suicide ideation, but not suicide plans or attempts among those with ideation. Instead, disorders characterized by severe anxiety/agitation (for example, post-traumatic stress disorder) and poor impulse control (for example, conduct disorder, substance use disorders) predict which suicide ideators who go on to make a plan or attempt. These results advance understanding of the unique associations between mental disorders and different forms of suicidal behavior. Future research must further delineate the mechanisms through which people come to think about suicide and progress from suicidal thoughts to attempts.Keywords: epidemiology; mental disorders; comorbidity; suicide; suicidal ideation; suicide attempt
Article
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The authors recently observed a correlation between state altitude and suicide rate in the United States, which could be explained by higher rates of gun ownership and lower population density in the intermountain West. The present study evaluated the relationship between mean county and state altitude in the United States and total age-adjusted suicide rates, firearm-related suicide rates, and non-firearm-related suicide rates. The authors hypothesized that altitude would be significantly associated with suicide rate. Elevation data were calculated with an approximate spatial resolution of 0.5 km, using zonal statistics on data sets compiled from the National Geospatial-Intelligence Agency and the National Aeronautics and Space Administration. Suicide and population density data were obtained through the Centers for Disease Control and Prevention (CDC) WONDER database. Gun ownership data were obtained through the CDC's Behavioral Risk Factor Surveillance System. A significant positive correlation was observed between age-adjusted suicide rate and county elevation (r=0.51). Firearm (r=0.41) and non-firearm suicide rates (r=0.32) were also positively correlated with mean county elevation. When altitude, gun ownership, and population density are considered as predictor variables for suicide rates on a state basis, altitude appears to be a significant independent risk factor. This association may be related to the effects of metabolic stress associated with mild hypoxia in individuals with mood disorders.
Article
Full-text available
Quantitative data on ventilation during acclimatization at very high altitude are scant. Therefore, we monitored nocturnal ventilation and oxygen saturation in mountaineers ascending Mt. Muztagh Ata (7,546 m). To investigate whether periodic breathing persists during prolonged stay at very high altitude. A total of 34 mountaineers (median age, 46 yr; 7 women) climbed from 3,750 m within 19-20 days to the summit at 7,546 m. During ascent, repeated nocturnal recordings of calibrated respiratory inductive plethysmography, pulse oximetry, and scores of acute mountain sickness were obtained. Nocturnal oxygen saturation decreased, whereas minute ventilation and the number of periodic breathing cycles increased with increasing altitude. At the highest camp (6,850 m), median nocturnal oxygen saturation, minute ventilation, and the number of periodic breathing cycles were 64%, 11.3 L/min, and 132.3 cycles/h. Repeated recordings within 5-8 days at 4,497 m and 5,533 m, respectively, revealed increased oxygen saturation, but no decrease in periodic breathing. The number of periodic breathing cycles was positively correlated with days of acclimatization, even when controlled for altitude, oxygen saturation, and other potential confounders, whereas symptoms of acute mountain sickness had no independent effect on periodic breathing. Our field study provides novel data on nocturnal oxygen saturation, breathing patterns, and ventilation at very high altitude. It demonstrates that periodic breathing increases during acclimatization over 2 weeks at altitudes greater than 3,730 m, despite improved oxygen saturation consistent with a progressive increase in loop gain of the respiratory control system. Clinical trial registered with www.clinicaltrials.gov (NCT00514826).
Article
Obesity increases the risk and severity of sleep-disordered breathing. The degree to which excess body weight contributes to blood oxygen desaturation during hypopneic and apneic events has not been comprehensively characterized. To quantify the association between excess body weight and oxygen desaturation during sleep-disordered breathing. A total of 750 adult participants in the Wisconsin Sleep Cohort Study were assessed for body mass index (BMI) (kg/m(2)) and sleep-disordered breathing. The amount of Sa(O(2)), duration, and other characteristics of 37,473 observed breathing events were measured during polysomnography studies. A mixed-effects linear regression model estimated the association of blood oxygen desaturation with participant-level characteristics, including BMI, gender, and age, and event-level characteristics, including baseline Sa(O(2)), change in Vt, event duration, sleep state, and body position. BMI was positively associated with oxygen desaturation severity independent of age, gender, sleeping position, baseline Sa(O(2)), and event duration. BMI interacted with sleep state such that BMI predicted greater desaturation in rapid eye movement (REM) sleep than in non-REM sleep. Each increment of 10 kg/m(2) BMI predicted a 1.0% (SE, 0.2%) greater mean blood oxygen desaturation for persons in REM sleep experiencing hypopnea events associated with 80% Vt reductions. Excess body weight is an important predictor of the severity of blood oxygen desaturation during apnea and hypopnea events, potentially exacerbating the impact of sleep-disordered breathing in obese patients.
Article
Studies assessing the effect of altitude on cardiovascular disease have provided conflicting results. Most studies were limited because of the heterogeneity of the population, their ecological design, or both. In addition, effects of place of birth were rarely considered. Here, we examine mortality from coronary heart disease and stroke in relation to the altitude of the place of residence in 1990 and at birth. Mortality data from 1990 to 2000, sociodemographic information, and places of birth and residence in 1990 (men and women between 40 and 84 years of age living at altitudes of 259 to 1960 m) were obtained from the Swiss National Cohort, a longitudinal, census-based record linkage study. The 1.64 million German Swiss residents born in Switzerland provided 14.5 million person-years. Relative risks were calculated with multivariable Poisson regression. Mortality from coronary heart disease (-22% per 1000 m) and stroke (-12% per 1000 m) significantly decreased with increasing altitude. Being born at altitudes higher or lower than the place of residence was associated with lower or higher risk. The protective effect of living at higher altitude on coronary heart disease and stroke mortality was consistent and became stronger after adjustment for potential confounders. Being born at high altitude had an additional and independent beneficial effect on coronary heart disease mortality. The effect is unlikely to be due to classic cardiovascular disease risk factors and rather could be explained by factors related to climate.
Article
In the United States, suicide rates consistently vary among geographic regions; the western states have significantly higher suicide rates than the eastern states. The reason for this variation is unknown but may be due to regional elevation differences. States' suicide rates (1990-1994), when adjusted for potentially confounding demographic variables, are positively correlated with their peak and capital elevations. These findings indicate that decreased oxygen saturation at high altitude may exacerbate the bioenergetic dysfunction associated with affective illnesses. Should such a link exist, therapies traditionally used to treat the metabolic disturbances associated with altitude sickness may have a role in treating those at risk for suicide.
Article
Patients undergoing dialysis at higher altitude receive lower erythropoietin doses, yet achieve higher hemoglobin concentrations. Increased iron availability caused by activation of hypoxia-induced factors at higher altitude may explain this finding. Hypoxia-induced factors are also involved in other pathways that may affect morbidity and mortality. To study whether mortality differed by altitude in patients initiating dialysis. Retrospective cohort of patients initiating dialysis in the United States between 1995 and 2004. Patients were stratified by the average elevation of their residential zip code. Covariates included age, sex, race, Medicaid coverage, dialysis modality, comorbidities, and reported laboratory measurements. We constructed proportional hazards models of all-cause mortality, stratifying by year, and censoring patients at 5 years from first dialysis, at the end of the database (December 31, 2004), or loss to follow-up. We also compared age- and sex-adjusted standardized mortality rates of US patients receiving dialysis with the general population. Mortality from any cause. A total of 804 812 patients initiated dialysis and were followed up for a median of 1.78 years. Crude mortality rates per 1000 person-years were 220.1 at an altitude lower than 76 m (<250 ft), 221.2 from 76 through 609 m (250-1999 ft), 214.6 from 610 through 1218 m (2000-3999 ft), 184.9 from 1219 through 1828 m (4000 to 5999 ft), and 177.2 at an altitude higher than 1828 m (>6000 ft). After multivariable adjustment, compared with patients living at an altitude of lower than 76 m, the relative mortality rates were 0.97 (95% confidence interval [CI], 0.96-0.98) for those living from 76 through 609 m; 0.93 (95% CI, 0.91-0.95), from 610 through 1218 m; 0.88 (95% CI, 0.84-0.91), from 1219 through 1828 m, and 0.85 (95% CI, 0.79-0.92) higher than 1828 m. Age- and sex-standardized mortality decreased more with altitude in patients receiving dialysis than in the general population. Altitude was inversely associated with all-cause mortality among US patients receiving dialysis.
Article
Personal anecdotes suggest that ascent to high altitude can cause mood changes such as depression, apathy, and drowsiness. Observed behaviors at high altitude indicate that people can become more euphoric, irritable, or argumentative. Since there are few systematic and quantitative studies assessing the effects of altitude on mood, this study compared moods measured at two different altitudes and times of day (morning-evening) using a standardized scale. Self-rated moods were determined twice daily in 19 males and 16 females with the Clyde Mood Scale. Baseline values were determined at 200 m; moods were then assessed at 4300 m with one group and at 1600 m with a second group. Friendliness, clear thinking, dizziness, sleepiness, and unhappiness were affected at 4300 m but only sleepiness changed at 1600 m. At 4300 m, the altered moods differed from baseline on the day of arrival (1-4 hours), differed even more after one day (18-28 hours), and returned to baseline by day 2 (42-52 hours). Morning and evening values were similar at each altitude. Therefore, changes in mood states at altitude have a distinct and measurable time course.