英语四级六级阅读(06)

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There are many known risk factors associated with suicide: those who take their own lives are statistically more likely to be white, male, and/or low-income. Surveys show that they are also more likely to have histories of depression, own fire arms and feel isolated. Many are divorced or have substance abuse problems. But a team of researchers found another risk factor that is less intuitive, even though it may be just as valid: living at a high altitude.

The team, lead by Dr. Barry Brenner from the University Hospitals Case Medical Center in Cleveland Ohio, analyzed 19 years worth of cause-of-death data from all 2,584 U.S. counties (between 1979 and 1998). In their study, published in High Altitude Medicine & Biology, they compared the 50 counties with the highest suicide rate to the 50 counties with the lowest, and found that county altitude was on average almost eight times higher in the areas with high suicide rates.

Even when the researchers controlled for five other suicide-related factors — two measures of income,race, age and population density of the county — the correlation was still strong. Wrote the scientists:

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 rearms, increased isolation, or reduced income. 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.

The authors note that there may be physiological reasons why high altitude may contribute to suicides; low barometric pressure in mountainous regions, for example, causes the body to become less efficient in transporting oxygen from the air, and these changes can affect brain functioning. In addition, they note, it's only suicides, and not other deaths that are positively associated with higher altitudes. While the results still need to be replicated, they at least suggest that achieving the "mountain high" may come at a dangerous price.