Positive Association between Altitude
and Suicide in 2584 U.S. Counties
and Carlos A. Camargo, Jr.
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 (r¼0.31,
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
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
Department of Emergency Medicine, University Hospitals Case Medical Center, Cleveland, Ohio.
Division of General Internal Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts.
HIGH ALTITUDE MEDICINE & BIOLOGY
Volume 12, Number 1, 2011
ªMary Ann Liebert, Inc.
hypothesized that counties at high elevation would have
higher suicide rates.
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
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.
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 (r¼0.31, 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
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).
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
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
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.
Controlling for percent of age >50 yr, percent male, percent white, median household income, median family income, and population
density of each county.
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 (r¼0.31).
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).
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
The authors have no conﬂicts of interest or ﬁnancial ties to
Baibas N., Trichopoulou A., Voridis E., and Trichopoulos D.
(2005). Residence in mountainous compared with lowland
areas in relation to total and coronary mortality. J. Epidemiol.
Comm. Health. 5(4):274–278.
Bloch K.E., Latshang T.D., Turk A.J., Hess T., Hefti U., Merz
T.M., Bosch M.M., Barthelmes D., Hefti J.P., Maggiorini M.,
and Schoch O.D. (2010). Nocturnal periodic breathing during
acclimatization at very high altitude. Am. J. Respir. Crit. Care
4 BRENNER ET AL.
CDC Suicide Mortality. Available <http://wonder.cdc.gov/
ICD9>. Accessed October 5, 2009.
CDC (Centers for Disease Control and Prevention). (1997). Re-
gional variation in suicide rate–United States, 1990–1994
Cheng D., Mendenhall T.I., and Brenner B.E. (2005). Suicide rates
strongly correlate with altitude. Acad. Emerg. Med. 12(suppl.
Daly M.C., Wilson D.J., annd Johnson N. (2007). Relative status
and well-being: evidence from US suicide deaths. Working paper
(2007-12). Available at <http://www.frbsf.org/publications/
Dumais A., Lesage A.D., Alda M., Rouleau G., Dumont M.,
Chawky N., Roy M., Mann J.J., Benkelfat C., and Turecki G.
(2005). Risk factors for suicide completion in major depression:
a case-control study of impulsive and aggressive behaviors in
men. Am. J. Psychiatry. 162(7):2116–2124.
Ellison L.F., and Morrison H.I. (2001). Low serum cholesterol
concentration and risk of suicide. Epidemiology. 12(2):168–
Faeh D., Gutzwiller F., and Bopp M. (2009). Lower mortality
from coronary artery disease and stroke at higher altitudes in
Switzerland. Circulation. 120(6):495– 501.
Goldsmith S. (2001). Risk Factors for Suicide: Summary of a
Workshop. Institute of Medicine, National Academy Press,
Haws C.A., Gray D.D., Yurgelun-Todd A., Moskos M., Meyer
L.J., and Renshaw P.F. (2009). The possible effect of altitude on
regional variation in suicide rates. Med. Hypotheses.
Hemenway D., and Miller M. (2002). Association of rates of
household gun ownership, lifetime major depression, and
serious suicidal thoughts with rates of suicide across US cen-
sus regions. Injury Prev. 8(4):313–316.
Kim N., Wade J., Brenner B.E., Haws C.A., Yurgelun-Todd D.A.,
and Renshaw P. (2011). Altitude, gun ownership, rural areas,
and suicide. Am. J. Psychiatry. In press.
Khoo M.C., Anholm J.D., Ko S.W., Downey R. III, Powles A.C.,
Sutton J.R., and Huston C.S. (1996). Dynamics of periodic
breathing and arousal during sleep at extreme altitude. Respir.
Maris R. (2001). Social and cultural factors in suicide risk. In:
Risk Factors for Suicide: Summary of a Workshop. Institute of
Medicine, National Academy Press, Washington, DC.
Mathers C.D., and Loncar D. (2006). Projections of global mor-
tality and burden of disease from 2002 to 2030. PLoS Med.
National Elevation Database. Available at <http://ned.usgs
.gov>. Accessed October 20, 2009.
Nicolas M., Thullier-Lestienne F., Bouquet C., Gardette B.,
Gortan C., Richalet J.P., and Abraini J.H. (2000). A study of
mood changes and personality during a 31-day period of
chronic hypoxia in a hypobaric chamber (Everest-Comex 97).
Psychol. Rep. 86(1):119–126.
Nock M.K., Hwang I., Sampson N.A., and Kessler R.C. (2010).
Mental disorders, comorbidity and suicidal behavior: results
from the National Comorbidity Survey Replication. Mol.
Peppard P.E., Ward N.R., and Morrell M.J. (2009). The impact of
obesity on oxygen desaturation during sleep-disordered
breathing. Am. J. Respir. Crit. Care Med. 180(8):788–793.
Rigby N.J., Kumanyika S., and James W.P., for the International
Obesity Task Force. (2004). Confronting the epidemic: the
need for global solutions. J. Public Health Policy 25(3):418–
Roth W.T., Gomolla A., Meuret A.E., Alpers G.W., Handke E.M.,
and Wilhelm F.H. (2002). High altitudes, anxiety, and panic
attacks: is there a relationship? Depression Anxiety. 16(2):51–
Shukitt B.L., and Banderet L.E. (1988). Mood states at 1600 and
4300 meters terrestrial altitude. Aviat. Space Environ. Med.
Shukitt-Hale B., Banderet L.E., and Lieberman H.R. (1998). Ele-
vation-dependent symptom, mood and performance change
by exposure to hypobaric hypoxia. Int. J. Aviat. Psychol.
Singh G.K., and Siahpush M. (2002). Increasing rural–urban
gradients in US suicide mortality: 1970–1997. Am. J. Public
Stack S. (2000). Suicide: a ﬁfteen year review of the sociologic
literature. Part 1: cultural and economic factors. Suicide Life
Threatening Behav. 30(2):145–162.
U.S. Department of Health and Human Services. Summary of
national strategy for suicide prevention: goals and objectives
for action. National Strategy for Suicide Prevention Web Site.
Available at <http:/www.mentalhealth.org/publications/
allpubs/SMAO1-3518/default.asp>. Accessed October 10,
U.S. Geological County Survey. Available at <http://.geonames
.usgs.gov/>. Accessed October 29, 2009.
U.S. Population Census. Available at <http://www.census.gov/
main/www/cen1990.html>. Accessed October 23, 2009.
West J.B., Peters R.M. Jr., Aksnes G., Maret K.H., Milledge J.S.,
and Schoene R.B. (1986). Nocturnal periodic breathing at al-
titudes of 6,300 and 8,050 m. J. Appl. Physiol. 61:280–287.
Winkelmayer W.C., Liu J., and Brookhart M.A. (2009). Altitude
and all-cause mortality in incident dialysis patients. JAMA.
Winslow R.M. (2007). The role of hemoglobin oxygen afﬁnity in
oxygen transport at high altitude. Respir. Physiol. Neurobiol.
Yu B.H, Ancoli-Israel S., and Dimsdale J.E. (1999). Effect of
CPAP treatment on mood states in patients with sleep apnea.
J. Psychiatr. Res. 33(5):427–432.
Zill P., Buttner A., Eisenmenger W., Moller H.J., Bondy B., and
Ackenheil M. (2004). Single nucleotide polymorphism and
haplotype analysis of a novel tryptophan hydroxylase isoform
(TPH2) gene in suicide victims. Biol. Psychiatry. 56(8):581–586.
Address all correspondence to:
Barry E. Brenner, MD, PhD
Department of Emergency Medicine
University Hospitals Case Medical Center
11100 Euclid Avenue
Cleveland, OH 44106
U.S. SUICIDE RATES INCREASE WITH ALTITUDE 5