Do highly religious people live longer lives? Previous research has suggested as much. A 2000 meta-analysis, which used data from 42 tests, concluded those deeply devoted to their faith were 29 percent more likely to be alive at any given follow-up point than their more secular peers.

But newly published research adds a large asterisk to those earlier findings. Using long-term data on the lives of 1,343 Americans born around the year 1910, a group of scholars found that, as expected, more-religious women lived longer than less-religious ones.

However, for reasons that remain unexplained, that equation did not hold true for men.

In a paper titled “Does Devoutness Delay Death?” published in the Journal of Personality and Social Psychology, a research team led by University of Miami psychologist Michael McCullough examined data from the Terman Life Cycle Study of Children with High Ability. First conducted in California in 1940 (with numerous follow-ups in the decades since), the study tracked the lives of more than 1,300 intellectually gifted men and women, all with IQs of 135 or higher.

Unsatisfied with previous research that measured religiosity at one point in subjects’ lives and assumed it stayed constant, McCullough and his colleagues used data from six waves of surveys (the last in 1991) to determine the trajectory of the participants’ spiritual lives. They then grouped the subjects into one of three classifications: high in religiosity, with devoutness gradually increasing through life (16 percent); consistently low in religiosity (39 percent); or those with a “parabolic” trajectory, featuring moderate religiousness in early adulthood which increased in midlife and then gradually decreased in old age (45 percent).

They found that women in the parabolic (or least-religious) class “had a higher hazard of dying at any point in the adult life course than did the women in the other two (more religious) classes.” In contrast, “men in the three trajectory classes did not differ in length of life.”

In another interesting finding, the researchers report that “getting married during one’s lifetime predicted longer life for people in the highly religious class, but not for people in the parabolic or least religious class, or for the sample overall.” They speculate that “perhaps marriage brings with it different health-relevant affordances for highly religious individuals than it does for less-religious individuals.”

They add that the religiousness-longevity connection most likely works both ways. Some personality traits, such as agreeableness, “incline people to live longer and to become more religious as they age,” they report. On the other hand, “religion may play a causal role” in good long-term health by facilitating social connections and discouraging destructive behavior such as alcohol abuse.

The researchers offer no answer as to why religiosity is associated with greater health benefits for women but not men. They point to a 2007 study of high-functioning older adults that found stress seems to take a lighter physical toll on religious women, but not men. But while that suggests a possible mechanism for explaining the longevity differences, it doesn’t answer the question of why. For now, the reasons for this surprising gender gap remain a mystery.

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