The Department of Defense and the Department of Veterans Affairs are beginning to examine sex differences, such as how psychologic and physical health conditions affect female soldiers and veterans, Nolan said. These agencies are also reporting when research shows no difference between the sexes.

Great strides have been made in raising public awareness about sex-based differences in cardiovascular, muscular, skeletal, and behavioral health and disease, but only rarely are medical-care options tailored to the patient’s sex, Nolan said. She suggested that it could take less time for research to be translated into medical practice if major journal publishers required analysis by sex and reporting of differences found or the lack thereof.

Barriers to Studying Sex Differences

There are both technical and political barriers to advancing knowledge of sex differences. Clancy described an imbalance between the fear of not knowing what the health-related differences between men and women are and the fear that identifying such differences is somehow impolitic or inappropriate. When the fear and concern associated with not knowing overpower concerns about the influence of politics on science, studying sex differences will become straightforward, she said.

There are methodologic challenges to studying population subgroups, such as males and females. A primary issue in breaking down data by sex is sample size. Berlin asked, Are two separate, adequately powered studies, one in each sex, needed? Or can a single study have sufficient statistical power to detect interaction? Separate studies of men and women risk confounding. Separate studies of men and women might use different doses as in, for example, studies of aspirin and myocardial-infarction prevention. It could then be difficult to tell whether differences in outcome were due to different doses, sex, or other factors. Instead, conducting two studies, each with both men and women, might allow stratification of both studies by sex and provide replication for sex-specific findings. Alternatively, meta-analytic principles could be applied to a program of development and testing.

A barrier to meta-analysis is availability of data. Clancy noted that the opportunity to conduct meta-analyses often rests on the goodwill of investigators in sharing data from clinical trials. As data collection has moved from paper to electronic form, the technical barriers to data-sharing have diminished. The unanswered question is who owns the data, particularly when studies have been funded with taxpayer dollars. With



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