Scientific American(Continued Page 2)
Gender Crossover
Surprisingly, as a group, men older than 90 generally have better mental function than do their female peers. Women, it seems, tend to live with their dementia rather than to die from it. In consequence, very old females on average retain less of their mental abilities than do men of the same age–who represent the healthy survivors left after other men susceptible to dementia have died off.
At later ages, men also do better than women in terms of physical health. Men in their sixties and seventies are more susceptible than are women to strokes and heart attacks. Delayed onset of these acute conditions allows women to survive longer than men who have to cope with disease earlier in life. In absolute numbers, many more women are still alive at 95, but in terms of average mental and physical health, men begin to take the lead. The healthy men who have generally avoided illnesses demonstrate a survival advantage over women: although men make up 20 percent of 100-year-olds, 40 percent of 105-year-olds are male. This switch to more mentally and physically fit men after age 90 constitutes what I have called a gender crossover.
Early signs of the gender crossover can be seen in studies of 80-year-olds. Men who survive to this age without major health problems often continue to live without needing special care. Richard M. Suzman and his colleagues at the National Institute on Aging found that men older than 80 years in one such study were more independent than were similarly aged women. Their 1984 report indicated that 44 percent of the men in that age group were robust and independent compared with only 28 percent of women in the same age group. Additionally, Kenneth G. Manton and Eric Stallard of Duke University estimated the active life expectancy–that is, the years of independent life left–for members of the U.S. senior population. Their findings showed that after age 85, men could expect to live a healthy and active life longer than women could.
What biological and environmental factors might allow the oldest old humans to reach age 95 and beyond in good health? Multiple and intertwined influences undoubtedly play important roles. So-called longevity genes seem to protect against the development of diseases; genetically or otherwise determined adaptive abilities enable survivors to avoid potentially life-threatening conditions. Modifications in everyday activities, such as not smoking, practicing better nutrition and exercising, may also help some people stay fit longer. Basic good luck surely helps as well.
Scientific American (Continued)
