One possible explanation for the surprising finding is that 'higher cognitive ability may be linked to behaviors that are conducive to good health, such as healthy eating, a low alcohol intake and avoidance of smoking,' the authors speculate.

Earlier research has shown a link between risk of death and poorer cognitive function in elderly people, which has been attributed to the brain degeneration that typically accompanies aging. But the findings regarding younger participants in the study were surprising.

. "These results suggest that reaction time is not merely an indicator of age-related physiological deteriorations but rather an indicator of the brain's more basic information-processing ability," say the authors, "suggesting that slower and more variable processing skills are a risk factor for mortality in themselves."

Beverly A. Shipley, PhD, of the University of Edinburgh in Scotland is lead author of the study, which is published in Psychosomatic Medicine.

Strong Association in Youngest, Oldest Groups

The researchers followed 6,424 subjects age 18 to 94 from the 1984-1985 UK Health and Lifestyle Survey to assess their scores on cognitive tests and risk of death over 19 years.

Between July 1985 and May 2003, 1,366 of the participants had died. Of these, 52 were age 20 to 29 years, 351 were ages 40 to 59 years, and 963 were age 60 and older.

In the youngest and the oldest groups, but not the middle group, a strong association was observed between risk of death and lower scores on simple reaction time (pressing a key after seeing a prompt); choice reaction time (pressing one of four keys after seeing a prompt); variability of reaction time; and, to a lesser degree, memory performance.

Cognitive Ability Linked to Healthier Choices?

The researchers considered the effects of other lifestyle factors associated with risk of death, such as smoking, heavy alcohol use and being overweight, before making a final determination regarding the link between cognitive scores and mortality risk.

Though the reasons for the association are unclear, "the cognition-mortality relationship may be explained in part by the brain's efficiency of information processing and memory performance," the authors suggest.

Another possible explanation may be that reaction time, which is linked with overall body deterioration, may be linked to brain functions associated with survival in the youngest group. For example, "higher cognitive ability may be linked to behaviors that are conducive to good health, such as healthy eating, a low alcohol intake and avoidance of smoking," say the authors.

Educational Interventions May Impact Public Health

The study is "of critical importance in public health." says Peter Muennig, MD, of Columbia University.

"If cognition is a major factor in determining human life expectancy, then education interventions have the potential for great public health impact," he notes.

"So far, there is good evidence that years of schooling prolongs life expectancy," Dr. Muennig points out. "This will make a strong contribution to this argument."