The risk of dying from cardiovascular disease（心血管疾病） is higher for childless men than for fathers, according to a large study led by a researcher at the Stanford University School of Medicine. The new study, which will be published online Sept. 26 in Human Reproduction, tracked some 135,000 male members of the American Association of Retired¹ Persons over a 10-year period, in order to determine whether the number of offspring a man has offers any clues about that man's long-term health. The findings show an association between parental² status and cardiovascular risk and should not be interpreted as proof of a cause and effect.

"This was the largest-ever study in the United States to examine the relationship between fatherhood and cardiovascular disease," said Michael Eisenberg, MD, assistant professor of urology（泌尿学） at Stanford. Moreover, the study was carefully controlled to minimize confounding variables that might otherwise cloud investigators³' capacity to generate meaningful results.

Eisenberg initiated⁴ the study while doing his urologic residency training at the University of California-San Francisco, and carried it through his joining the faculty⁵ at Stanford. (The paper's senior author is Mark Pletcher, MD, MPH, associate professor of epidemiology & biostatistics at UCSF.) He had wondered whether infertile⁶ men's long-term health outcomes might differ from those of fertile men, and he reasoned that the number of offspring a man fathered could be a rough proxy⁷ for ability to reproduce.

"So we asked: Is not having children a predictor of death from cardiovascular disease?" he said.

To find out, Eisenberg and his associates pored over data compiled from a series of questionnaires that hundreds of thousands of AARP members had completed over a period of about 10 years. The scientists narrowed their health-outcome analysis to some 135,000 married or formerly⁸ married men (about 95 percent of them white) who were all over age 50 when the study began. Their median age at the start of the study was 62.7 years old.

To ensure, as much as possible, that the men they were looking at had both the intent and the opportunity to reproduce, Eisenberg and his colleagues restricted their sample population to those who were married or had once been married. To further level the playing field, they also excluded men with any previous history of various health conditions including heart disease, stroke or a related condition, which could have impeded⁹ successful reproduction. The resulting subject group was thus in a state of relatively¹⁰ good initial health.

Over the study's duration, the investigators tallied¹¹ mortality from between 60 and 70 different causes. Deaths were assessed via various methods including through Social Security Administration and other national databases as well as surviving relatives' responses to mailed questionnaires.

Next, all participants living or dead were grouped according to the number of children they had fathered, and mortality rates within each group were calculated. In their statistical¹² analysis, Eisenberg and his colleagues corrected for body-mass index, self-reported activity levels and health status, tobacco and alcohol use, race, age, median household income, and education.

Over the course of the study, about 10 percent of the men died. About one in every five of those deaths was attributable to cardiovascular disease. That represented a 17 percent increase in the likelihood of a childless man's dying of a condition related to cardiovascular disease, compared with fathers.

The genders¹³ of the children a man had fathered made no difference in the likelihood of his succumbing¹⁴ to（屈服于） cardiovascular disease.