Over the past decade, women’s health has emerged as a rapidly expanding field of scientific inquiry and knowledge with important implications for clinical practice and for the education and training of physicians. The increasing scientific information about the influence of gender differences on health and disease has expanded our concept of women’s health beyond the traditional focus on reproductive organs and their function. Women’s health can be viewed broadly as the study of the effect of sex and gender on health and disease that occurs across the spectrum of the biologic, behavioral, and social sciences. This broader interdisciplinary perspective of women’s health has created an area of new knowledge and scholarship that is distinct from or more detailed than the knowledge base of existing disciplines. It has provided a new model by which to study the interactions between biologic mechanisms and psychosocial and environmental factors and their influence on human growth and development and response to health challenges. The clinical application of this information to women across all age groups highlights the interdisciplinary nature of this field.

The concept of women’s health requires a reassessment of the importance of gender differences on health and disease. Complex interactions exist between sex hormones, normal and abnormal physiology, and the physical and emotional well-being of women. As early as the embryonic period, there are structural differences between female and male brains. Many of these differences are programmed during fetal life by hormones. During the reproductive years, the influence of sex hormones on sexual development and reproductive function differentiates a category of health issues that are unique to women. As women age and sex hormones decrease during the menopause, women’s risk factors for disease change dramatically and become more similar to men’s. Although women develop the diseases that affect men, biologic mechanisms and psychosocial factors influence the course of disease differently in women.

Until recently, most of the information used to make clinical decisions in women was based on studies conducted primarily in men. Women were excluded from research on diseases that are important to both sexes because of misconceptions about women’s health, legal and ethical issues, and cultural biases. Because women, on average, live longer than men and are affected by major diseases at a later age, it was often perceived incorrectly that women were healthier than men. In fact, throughout life women experience poorer health than men, especially in the advanced years. The lack of information concerning women had important implications. Information based primarily on studies done in men was often applied inappropriately to women or resulted in different standards of care.

Efforts to increase our knowledge about women’s health issues require an integrated approach that acknowledges the diversity among women and considers the social factors that influence their lives. One of the important social trends over the past 50 years is the increasing participation of women in the work force. Since World War II, the number of women who work has more than doubled and is expected to exceed 80% by the end of the 20th century. The full effects of multiple roles, work stress, and new environmental exposures on women’s health and reproductive status are largely unknown but are certain to have important health and social ramifications. Paralleling the growing numbers of women in the work force is the increasing number of single-parent families headed by women, especially minority women. Many of these families live in poverty. Increasing evidence indicates that socioeconomic factors are major indicators of health and that, for some health outcomes, poverty and lack of education are more important determinants of health than ethnicity. However, important ethnic and racial differences remain in women’s susceptibility and response to certain diseases that cannot be explained wholly by socioeconomic status. For example, mortality rates for coronary heart disease, stroke, and breast cancer are higher in black than in white women, whereas death rates from lung cancer are higher in white women.

The increasing diversity of the population will affect health trends in the United States and the health status of women specifically. Regardless of their minority group, ethnic minority women have a lower life expectancy than white women and experience greater health problems. These differences are most pronounced in areas related to reproductive issues and childbearing, the occurrence and course of chronic disease, the incidence and outcome of cancer, and acts of interpersonal violence. Along with changes in our society, human immunodeficiency virus (HIV) infection and homelessness have become additional special health concerns of minority group women.

One of the most important factors underlying the current interest in women’s health is the increasing number of women entering the health professions, especially the discipline of medicine. Since the early 1900s, the proportion of women represented in the physician population increased threefold, from 6 to 17%. According to projections, this proportion will increase to 30% early in the 21st century. Already, women comprise over 40% of entering medical students and over 50% of minority graduates from medical schools. Although significant barriers remain to their attaining equal professional and academic status, the potential for women to influence the structure of their profession, the delivery of health care, and the direction of medical research is considerable.

At the turn of the century the average life span of women in the United States was 48 years, compared with 46 years in men. Since then the life expectancy in women has almost doubled and is now 79 years, compared with 73 years in men. Because of the gender gap in life expectancy, women currently comprise close to two thirds of the population older than age 65 and three fourths of the population older than age 85. The fastest-growing age group in the United States is the population aged 85 years and older. As a result, it is estimated that at the beginning of the 21st century, women will outnumber men by 2 to 1 in the age groups older than 65 and by 3 to 1 in the population older than 85. The reasons for the dramatic increase in overall life expectancy are thought to be related to the control of infectious diseases and progress in the treatment of chronic diseases such as diabetes and cardiovascular disease. The reasons for the disparity in life expectancy in women and in men are less well established but are thought to be primarily biologic.

Despite a dramatic decline in mortality rates for heart disease that has occurred in both sexes over the past two decades, heart disease remains the leading cause of death in women and accounts for one third of all deaths in women. Heart disease occurs about 10 years later in women than in men. This delayed onset is thought to be due primarily to the protective effect of estrogens in premenopausal women and accounts for the fact that 90% of heart disease mortality in women occurs after the menopause. There are significant racial and ethnic differences in mortality among women. Black women are more likely to die of heart disease than white women up to age 75; thereafter, death rates are higher in white women. In contrast, Hispanic and Native American women have significantly lower rates of death from heart disease. Evidence suggests that heart disease, once it develops, is more serious in women than in men, resulting in higher mortality rates. In addition to biologic factors, the poorer survival of women may be due to the older age and increased prevalence of co-morbid conditions in women at the time of diagnosis, as well as to less well-defined social factors that influence the diagnosis and treatment of heart disease in women.

Cancer is the second leading cause of death in women and is the most common cause of premature death. The mortality rate for all cancers combined in women has changed little during the last part of the 20th century. Major advances in the diagnosis and treatment of cervical and uterine cancers in women have been offset by an increase in mortality rates for lung and breast cancer. Although breast cancer is still the most common cancer diagnosed in women, lung cancer is now the leading cause of cancer deaths. Unfortunately, most of these deaths can be attributed to cigarette smoking. Whereas deaths from lung cancer in men have begun to decline due to a decrease in male cigarette use, death rates for women increased between 1990 and 1995 and are expected to continue to rise.

Breast cancer is the second leading cause of cancer deaths in women. Although the incidence of breast cancer has risen over the past decade, mortality rates have remained relatively stable. This disparity is thought to be caused partly by the widespread use of screening mammography and the detection of earlier-stage cancers that have a more favorable prognosis. There are significant age and racial differences in breast cancer mortality. Declining mortality rates in younger women have been offset by an increase in mortality rates in older women. Although breast cancer incidence rates are 12% lower in black than in white women, mortality rates are 15% higher in black women. Reasons for racial differences in breast cancer incidence and mortality are unclear but may be related to socioeconomic and biologic factors as well as certain health behaviors, such as participation in screening mammography. Although it has been shown that breast cancer screening with mammography and clinical breast examination decreases mortality from breast cancer in women older than age 50 by approximately 30%, less than 50% of American women aged 50 years and older receive regular screening; and this figure is considerably lower in poor, minority, and elderly women. Read more: risk factors for breast cancer.

Although stroke-related deaths have declined by almost 60% in the United States over the past 25 years, deaths from stroke still account for approximately 6% of all deaths in women and rank third as a cause of mortality. Striking racial differences exist in stroke mortality: death rates in black women are almost twice those for white women. Most of the stroke deaths in women result from thromboembolic disease and occur in older women. However, subarachnoid hemorrhage, the least common form of stroke, is more common in women than in men and contributes to stroke mortality, particularly in younger women.

Death rates from chronic pulmonary diseases have increased steadily for both women and men during the past 25 years; however, the increase has been greater in women. Because this increase has been linked to patterns in cigarette smoking, the increase in death rates in women for pulmonary disease, as well as for lung cancer, are expected to continue to rise. Death rates from pneumonia and influenza closely parallel pulmonary-related deaths and vary over time based on the epidemiology of these acute illnesses.

Diabetes has consistently ranked as a leading cause of death in women. Moreover, the reported death rate from diabetes most likely underestimates the impact of this disease on mortality because of its strong association with other life-threatening medical conditions, such as cardiovascular disease, stroke, and kidney failure. It is estimated that diabetes affects one in six women older than age 45; however, prevalence rates are higher in black, Hispanic, and Native American women. Separate from disease-related death rates, diabetes is a significant cause of morbidity and, in women of childbearing age, has important adverse effects on pregnancy outcome, resulting in an increased risk of fetal and perinatal mortality as well as congenital malformations.

Although HIV infection is not one of the 10 leading causes of death in women overall, it is responsible for the largest percent increase in death rates of all the major causes of mortality. HIV-related mortality rates are nine times higher for black than for white women. As a result, HIV infection ranks third as the leading cause of death in black women ages 15 to 24 and first in the age group 25 to 44 and in some geographic areas has become the number one cause of death. As the epidemiology of this epidemic changes, with heterosexual transmission accounting for an increasing proportion of HIV infection in women, these rates are expected to continue to rise.

Mortality rates alone do not provide a complete picture of women’s health status. Although women live longer than men, overall measures of health status are worse in women. Based on estimates from the National Health Interview Survey (NHIS), more women than men report symptoms or seek care for acute medical conditions, such as respiratory and digestive disorders, and are more disabled by these self-limited illnesses, as measured by number of days spent in bed or days lost from work. In addition, several chronic conditions occur more frequently in women and cause significant disability, such as arthritis, thyroid disease, migraine, bladder disorders, gastritis, colitis, and chronic constipation. Data from other sources show that affective disorders, especially major depressive episodes, and the anxiety disorders are significantly more prevalent in women. Most importantly, women’s self-perceived health status is poorer than men’s. According to estimates from the NHIS, only 36% of women describe their health as excellent, compared with 41% of men.