Sex differences in illness incidence, prognosis and mortality: Issues and evidence

Abstract This paper reviews current research and presents new evidence concerning sex differences in morbility and mortality. Attention is focused primarily on the following topics: (1) sex differences in incidence, prognosis and mortality for several major types of chronic disease, (2) causes of sex differences in morbility and mortality, (3) sex differences in physician visits and (4) a methodological issue, whether there are sex differences in reporting morbility. Relationships between sex differences in incidence, prognosis and mortality have been analyzed for various types of cancer, ischemic heart disease and rheumatoid arthritis. There was little or no correlation between sex differences in incidence and sex differences in prognosis. Sex differences in prognosis were generally smaller than sex differences in incidence. In most cases, sex differences in prognosis made a relatively small contribution to sex differences in mortality, and sex differences in incidence were the primary determinant of sex differences in mortality. These patterns indicate that the causes of sex differences in incidence frequently have little effect on sex differences in prognosis. Reasons for this are discussed in the text. The causes of sex differences in morbility and mortality are discussed, with attention to the contributions of genetic and environmental factors, sex roles, sex differences in stress responses and sex differences in risk-taking and preventive behaviors. One conclusion is that, although men take more risks of certain types, there does not appear to be a consistent sex difference in propensity to take risks or to engage in preventive behavior. Rather sex differences in risk-taking and preventive behavior vary depending on the specific behavior and the culture considered. Sex differences in physician visit rates are influenced by a variety of biological and cultural factors. For example, women's more complex and demanding reproductive functions are a major reason for women's higher rates of physician visits, at least in Western countries. The importance of cultural factors is indicated by the cross-cultural and historical variation in sex differences in physician visit rates. In order to test whether there are sex differences in the reporting of health and illness, discrepancies between self-report and medically-evaluated morbidity measures have been assessed for males and females in twelve studies. These data indicate that sex differences in reporting vary depending on the particular type of morbidity measure considered. For example, for self-ratings of general health women may be more predisposed than men to rate their health poor, but no significant sex differences were observed in reporting of physician visits or hospital admissions. The evidence discussed in this paper illustrates the diversity and complexity of factors that influence sex differences in morbidity and mortality. A major challenge for research in this area is to derive explanations of sex differences in morbidity and mortality that are as broad and general as possible and yet take adequate account of the real complexity of the data.