Although life expectancy at birth of women in western societies is significantly longer than that of men (e.g., 80 versus 74 years in the United States), women experience more sickness and non-fatal health problems than men (e.g., higher morbidity). Specific biological and behavioral explanations for these gender differences are largely unknown. It remains unclear whether these gender differences in health and mortality are found throughout the world. Here, the term ‘‘gender’’ refers to the way biological differences are socially and culturally constructed and expressed in actions and thoughts, whereas the term ‘‘sex’’ is used to define a biological category based on anatomical and physiological differences between males and females. ‘‘Health’’ is a state of complete physical, mental, and social wellbeing and not merely the absence of disease or infirmity, according to the World Health Organization (WHO). ‘‘Mortality’’ is the rate of death in a population in a specified time period.
In the year 2000, the overall life expectancy at birth ranged from a high of 81.1 years in Japan (84.7 for women and 77.5 for men) to a low of 37.5 years in Malawi (37.8 for women and 37.1 for men), as measured from the 191 Member States of the WHO. At the beginning of the twentieth century female life expectancy exceeded male life expectancy by only 2–3 years in Europe, North America, and Australia, whereas at the beginning of the twenty first century this gender related difference in life expectancy was more than 10 years in some countries. Fewer deaths in childbirth help women today to live longer, accounting in part for the increase in the gap between male and female longevity. Worldwide analysis reveals a few exceptions: male life expectancy is higher than that of women (by less than a year) in a few countries (including Botswana, Namibia, and Nepal). These mortality sex differences prevail at all ages, races, and social conditions. In 2002, worldwide, the four leading causes of disease burden (premature death and disability) over age 15 included HIV/AIDS, coronary heart disease, cerebrovascular disease, and unipolar depressive disorders. More specifically, HIV/AIDS was the leading disease burden for males and the second leading one for females (7.4 percent and 7.2 percent). The number one disease burden in females was unipolar depressive disorders (8.4 percent), whereas this disease ranked fourth for males (4.8 percent). Thus, of the four major causes of disease burden, unipolar depressive disorders have the greatest gender specific difference. Coronary heart disease and cerebrovascular disease were the second and third most common cause for males (6.8 percent and 5.0 percent), and the third and fourth most common cause for females (5.3 percent and 5.2 percent). In conclusion, unipolar depressive disorders affected women relatively more than men, while coronary heart disease was somewhat more prevalent among men.
Women experience more poor health during their lives than do men. This gender difference in overall health is assessed by determining the number of days confined to bed, the frequency of sick leave from work, rates of yearly doctor and hospital visits, and the number of self-reported disease symptoms. For example, in the 1991 US National Health Interview Sur vey, the total proportion disabled (reporting difficulty with one or more activities of daily living) was nearly twice as high for women as men. However, the finding that women experience more health problems than men is being challenged with recent research documenting a more nuanced picture of gender differences in health, at least within developed western societies. For example, one study found no consistent gender differences in reported health symptoms for young people in England. Another study, based on men and women working full time for an English bank, found difference by sex in symptoms of malaise (e.g., difficulty sleeping, nerves, and always feeling tired), but not in physical symptoms (e.g., hay fever, constipation, and a bad back) or in minor psychiatric morbidity (a 12 item general health questionnaire). The hypothesis that women are more willing to acknowledge and report poor health has also not been supported consistently in recent studies.
More research is needed to better understand the prevalence and causes of these general health differences between men and women. Future research will benefit from the use of health indices that have been evaluated for their validity and reliability in different research settings in order to ensure that findings between countries and across time are comparable and generalizable. In addition, the accuracy and completeness of health and mortality statistics are crucial in determining sex or gender differences. For example, measured differences might be the result of incomplete coverage of national death statistics, interviewer bias in health survey data, or because hospital and clinical data on disease include only the population attending these institutions, although women and men may be differentially admitted and treated.
Differing life span and quality of health can be due to biological factors, but medical research has not always accounted for sex differences. In 1977, in response to the adverse events following use of thalidomide and diethylstilbestrol in pregnant women, the US Food and Drug Administration (FDA) issued guidelines recommending that women in their childbearing years be excluded from phase 1 clinical trials (safety evaluations of new drugs based on healthy subjects). On scientific grounds it was justified to exclude women as clinical research participants because it was believed that men and women did not differ significantly in response to treatment in most situations, and the inclusion of women would introduce additional noise (from the hormonal variations caused by the menstrual cycle) and increase the heterogeneity of the study population. These faulty assumptions led to a period in which women were under represented in research subject populations, a trend that may have reduced the effectiveness of new therapeutics for female patients. Thus, in 1985, the US Public Health Service Task Force on Women’s Health Issues concluded that health care for women and the quality of health information available to women had been compromised by the historical lack of research on women’s health. In 1993, with the National Institutes of Health Revitalization Act, the guidelines for inclusion of women became law and the FDA lifted the 1977 restrictions. In 1998 the FDA issued a rule allowing the agency to refuse new drug applications that did not appropriately analyze safety and efficacy data by sex.
In 2001 the Institute of Medicine formed a Committee on Understanding the Biology of Sex and Gender Differences, which found evidence suggesting that published research frequently did not present findings by sex, even though the data were available. It was noted that research on women’s health and the inclusion of women in clinical trials would have limited value unless the actual differences between males and females were systematically studied and reported in published research. This committee noted that a number of sex based differences in health are attributable to sexual genotype (XX in the female and XY in the male on the 23rd chromosome pair) and hormonal or genetic differences between the two sexes. Also, men and women have dissimilar exposures (e.g., work and leisure activities), susceptibilities, and responses to initiating agents. Finally, sex differences in energy storage and metabolism result in variable responses to pharmacological drugs and the development of diseases such as obesity, autoimmune disorders, and coronary heart disease.
Examining the different experience of men and women with a particular disease, such as coronary heart disease, illustrates the complex effects of sex and gender on health, as well as the need for more research. Coronary heart disease begins in utero, evolves through child hood and young adulthood, and becomes a serious and often fatal health problem in middle and old age. Plaques of cholesterol and other cellular materials are deposited in the coronary arteries of the heart and over time compromise the flow of blood, causing cell and organ death (myocardial infarction). In general, men manifest symptoms 10–20 years earlier than women, have higher prevalence of primary risk factors, and die at earlier ages, although women who have had a myocardial infarction are much more likely to die within a year compared to men. Female sex hormones (estrogen) reduce women’s risk of coronary heart disease, in part by mitigating negative effects of serum lipids (fats in the bloodstream), while men’s higher testosterone levels have unfavorable effects on serum lipids. In many non-industrial societies, sex differences in cholesterol levels are minor or absent, largely an effect of diets low in saturated fats. It might also be that sex differences in serum lipid levels are linked to body composition, men having more abdominal fat, whereas women have more hip and thigh fat.
Several longitudinal studies, such as the Framingham Heart Study (US), the Tromso Heart Study (Norway), and the National Health and Nutrition Examination Survey (US), documented that genetics, age, and environmental and lifestyle factors are associated with onset of coronary heart disease. For example, environ mental agents such as smoking, diet high in calories and saturated fat, obesity, a sedentary lifestyle, and psychosocial stress are linked to high blood pressure, high cholesterol, and diabetes. These factors are risk factors for coronary heart disease in both males and females, although susceptibilities and responses vary by sex. However, these studies did not explain why such sex differences exist. Smoking is a strong risk factor for coronary heart disease and the increase in smoking among women relative to men has contributed to narrowing the gap between men and women in mortality from coronary heart disease. There is evidence suggesting that medical care reduces coronary heart disease mortality more for men than for women, at least in the US. Women’s com plaints about chest pains tend to get cursory attention and women are less likely to get diagnostic evaluations. The data indicate that women get treatment at more advanced disease stages and more often have emergency surgery. Finally, heart conditions often present different symptoms in men and women, but more is known about this disease in men, in part because women often were excluded from clinical trials and epidemiological studies. Results from research on men have simply been extended and applied to women, although it is now acknowledged that men and women have different exposures to risk factors and respond differently to some of the same risk factors. This underscores the importance of designing studies that address heart disease risk factors, treatment, and prevention in women.
Men and women respond differently to stress (the perception of excessive demands with which an individual is unable to cope), which is a risk factor for coronary heart disease. Lack of control induces stress and evidence suggests that women experience less control than men. In general, women experience more stress from their work because they have relatively lower status jobs with less control, less security, and less financial reward. In addition, women usually take on a greater burden of household chores, including childcare. Women do report more stress than men, but it has been argued that women simply express their distress more than men. Recent research showed that women are not socialized to complain more than men (express more stress), although it is possible that women and men feel differently about expressing emotional problems. Thus, there is accumulating evidence from western societies that women encounter more stress than men in their daily lives. Hence, stress might be a more important risk factor for coronary heart disease for women than men, although the higher levels of estrogen somewhat protect women from the negative effects of stress.
The question is whether the effect of stress on cardiovascular health is different for women and men. Laboratory studies showed that men express greater adrenaline response to stress than women, and it is hypothesized that women are protected against elevation of adrenaline because of higher levels of circulating estrogen. Elevated levels of circulating adrenaline may be bad for cardiovascular health because adrenaline stimulates the release of metabolites that contribute to raising levels of serum cholesterol. In addition, adrenaline is involved with the regulation of blood pressure, and repeated high blood pressure may lead to sustained hypertension. Studies of men and women in a number of non-manual occupations showed significantly higher adrenaline levels in men on working days than on weekends, but no such difference for women. Furthermore, self-reported stress experienced on rest and work days was significantly associated with adrenaline response in men, but not in women. This difference in adrenaline response was seen, even though women and men reported (by questionnaire) similar levels of stress on workdays and the weekend and both sexes reported higher stress on workdays. Men and women also reported similar mood states, with the exception that men’s anxiety dropped after work, while women’s did not change. Thus, differences in subjective experience could not explain differences in adrenaline response to work between men and women, suggesting the influence of biological mechanisms. In summary, sex differences in coronary heart disease and mortality appear to be due to the interaction of multiple biological and behavioral factors.
Despite the importance of understanding why women live as much as 10 years longer than men and why women experience poorer health throughout their lives, so far no behavioral or biological explanation adequately explains this paradox. It is unlikely that biological and acquired risk differences fully explain why women experience poorer health, but live longer, for psychosocial aspects of symptoms and health care seeking (illness behavior) might play an important role.
References:
- Howson, P., Harrison, P. F., Hotra, D., & Law, M. (Eds.) (1996) In Her Lifetime: Female Morbidity and Mortality in Sub Saharan Africa. Institute of Medicine, National Academy Press, Washington, DC.
- Hunt, K. & Annandale, (Eds.) (1999) Special Issue: Gender and Health. Social Science and Medicine 48(1):1-138.
- Lopez, D., Ahmad, O. B., Guillot, M., Ferguson, B. D., Salomon, J. A., Murray, C. J. L., & Hill, K. H. (2002) World Mortality in 2000: Life Tables for 191 Countries. World Health Organization, Geneva, pp. 11-14.
- Pollard, T. M. & Hyatt, S. B. (Eds.) (1999) Sex, Gender and Health. Biosocial Society Symposium Cambridge University Press, Cambridge.
- Wizemann, M. & Pardue, M. L. (2001) Exploring the Biological Contributions to Human Health: Does Sex Matter? Institute of Medicine, National Academy Press, Washington, DC, pp. 21-6.
- World Health Organization (2003) World Health Report 2003: Shaping the Future. World Health Organization, Geneva, 14.
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