January 19, 2011 — A new study provides more evidence that individuals who live at higher altitudes may be at increased risk for suicide.
Barry E. Brenner, MD, PhD, of University Hospitals Case Medical Center, Cleveland, Ohio, and colleagues, found that people living at higher elevations in the United States had statistically significantly higher rates of suicide.
This finding was not explained by county differences in demographic factors, income, geographic isolation, or greater access to firearms.
"This is a real phenomenon," Dr. Brenner told Medscape Medical News.
The study was published online January 7 in the journal High Altitude Medicine & Biology.
It is known that suicide rates in the United States are among the highest in the western mountainous states, including Utah, Colorado, Montana, and Nevada.
Two recent preliminary studies that found a positive correlation between altitude and suicide relied on the average or highest state altitude, or the elevation of the state capital city, to represent the altitude of the entire state.
However, US states vary greatly in altitude, and this method severely minimizes this variation, Dr. Brenner's team points out. Because counties vary considerably less in altitude than an entire state, they reexamined the altitude-suicide link at a county level.
The investigators included all 2584 US counties in their analysis. They examined county-specific mortality data for 20 years (1979-1998) and determined altitude for each county using the US Geologic Survey.
During the study period, among 42,868,100 total deaths, there were 596,704 suicide deaths (1.4%).
There was a negative correlation between county altitude and all-cause mortality (r = −0.31; P < .001), yet a "strong positive correlation" between county altitude and suicide rate (r = 0.50; P < .001). Positive correlations were seen for both firearm-related suicides (r = 0.40; P < .001) and non–firearm-related suicides (r = 0.31; P < .001).
Prior reports of increased suicide rates in the US mountainous region have fueled speculation that the excess may be due to greater access to firearms, increased isolation, or reduced income. But even after controlling for these variables, the positive correlation between altitude and suicide still exists, they report.
The association also remained strong after controlling for the percentage of county residents older than 50 years, percentage male, percentage white, median household income, and population density of each county.
8-Fold Difference in Risk
According to the researchers, there was an 8-fold difference in altitude in the 50 counties, with the highest suicide rates relative to the 50 counties with the lowest suicide rates (4684 vs 582 feet). The threshold value for increased suicide rates occurred in the range of about 2000 to 3000 feet above sea level.
Altitude-induced hypoxia is 1 potential mechanism for the altitude-suicide link. Chronic hypoxia is also thought to increase mood disturbances. The 2may work in concert. Increased metabolic stress at high altitude is another potential factor.
At the moment, the why is a "big black box," Dr. Brenner said. Pinpointing what's behind the altitude-suicide link "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.
"People who are suffering from severe depression or having suicidal thoughts at high altitude may do better to descend," Dr. Brenner said. "Not everyone can adjust to all aspects of high-altitude living. There may be certain times in their lives when it may be better to descend, but all this is unclear at the moment."
Dr. Brenner's team says future studies outside the United States may or may not confirm the altitude-suicide association. Should the association not be seen outside the United States, "it is possible that our findings are owing to conditions that are more common in the US."
But Dr. Brenner told Medscape Medical News that a paper to be published soon will show a similar link between high-altitude living and suicide in all 233 counties in South Korea.
The study authors have disclosed no relevant financial relationships.
High Altitude Med Biol. Published online January 7, 2011.
Medscape Medical News © 2011 WebMD, LLC
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Cite this: High-Altitude Living an Independent Suicide Risk Factor - Medscape - Jan 19, 2011.