The emergence of men’s health as a distinct discipline within internal medicine is founded on the evidence that men and women differ across their life span in their susceptibility to disease, in the clinical manifestations of the disease, and in their response to treatment. Furthermore, men and women weigh the health consequences of illness differently and have different motivations for seeking care. Men and women experience different types of disparities in access to health care services and in the manner in which health care is delivered to them because of a complex array of socioeconomic and cultural factors. Attitudinal and institutional barriers to accessing care, fear and embarrassment due to the perception by some that it is not manly to seek medical help, and reticence on the part of patients and physicians to discuss issues related to sexuality, drug use, and aging have heightened the need for programs tailored to address the specific health needs of men.
Sex differences in disease prevalence, susceptibility, and clinical manifestations of disease were discussed in Chap. 6e (“Women’s Health”). It is notable that the two leading causes of death in both men and women—heart disease and cancer—are the same. However, men have a higher prevalence of neurodevelopmental and degenerative disorders; substance abuse disorders, including the use of performance-enhancing drugs and alcohol dependence; diabetes; and cardiovascular disease; and women have a higher prevalence of autoimmune disorders, depression, rheumatologic disorders, and osteoporosis. Men are substantially more likely to die from accidents, suicides, and homicides than women. Among men 15–34 years of age, unintentional injuries, homicides, and suicides account for over three-fourths of all deaths. Among men 35–64 years of age, heart disease, cancer, and unintentional injuries are the leading causes of death. Among men 65 years of age or older, heart disease, cancer, lower respiratory tract infections, and stroke are the major causes of death.
The biologic bases of sex differences in disease susceptibility, progression, and manifestation remain incompletely understood and are likely multifactorial. Undoubtedly, sex-specific differences in the genetic architecture and circulating sex hormones influence disease phenotype; additionally, epigenetic effects of sex hormones during fetal life, early childhood, and pubertal development may imprint sexual and nonsexual behaviors, body composition, and disease susceptibility. Reproductive load and physiologic changes during pregnancy, including profound hormonal and metabolic shifts and microchimerism (transfer of cells from the mother to the fetus and from the fetus to the mother), may affect disease susceptibility and disease severity in women. Sociocultural norms of child-rearing practices, societal expectations of gender roles, and the long-term economic impact of these practices and gender roles also may affect disease risk and its clinical manifestation. The trajectories of age-related changes in sex hormones during the reproductive and postreproductive years vary substantially between men and women and may influence the sex differences in the temporal evolution of age-related conditions such as osteoporosis, breast cancer, and autoimmune disease.