The death rate for people who never had children was up to 4 times higher than that of biological and adoptive parents.

PROBLEM: Having a child, it's been observed, appears to lessen one's risk of premature death. Might parenthood be somehow protective, or is this just a simple case of confounding variables, where there's some factor that makes those more likely to die earlier also less likely to become parents?

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METHODOLOGY: Danish researchers turned a group of 21,276 couples undergoing IVF treatment for infertility over a 14-year period into a "natural experiment," by comparing those who ended up having children to those who did not. Over 15,000 children were eventually born the couples, while another 1500 were adopted.

RESULTS: The death rate for childless women was 4 times higher than for women who had given birth. Women who had adopted had two-thirds the likelihood of dying prematurely. The death rate was also approximately halved for both biological and adoptive fathers. When the researchers controlled for things like age, education level, and income, these differences remained significant.

All of the deaths were attributed to circulatory disease, cancers, or accidents.

CONCLUSION: While unable to prove causation, the authors concluded that mortality rates are higher in people who don't have children.

IMPLICATION: Because this study looked at people who were involuntarily childless, it weeded out factors like low levels of social support or unhealthy behavior that might have caused those who never had children to die earlier. However, it can't rule out everything. That adoptive parents had higher survival rates, for example, may be due to the fact that they had to pass evaluations of their health and socioeconomic status before they were allowed to adopt.

The full study, "Childlessness, parental mortality and psychiatric illness: a natural experiment based on in vitro fertility treatment and adoption," is published in the Journal of Epidemiology and Community Health.