- Cholesterol
- Smoking
- High Blood Pressure
- Obesity
- Physical Inactivity
- Hormonal Changes
- Diabetes mellitus
It is generally accepted that many factors contribute to CHD in both men and women, including cholesterol, smoking, high blood pressure, obesity and physical inactivity, although they may differ in relative importance. Hormone levels are an added element for women. The effects of the menopause and hormone therapy on heart disease are only now receiving the attention necessary to determine how prevention and treatment of CHD may differ for women.
Comparisons among women in several European countries also suggest substantial roles for genetic and environmental factors. In terms of CHD incidence, women are closer to men in the same country than they are to women in other countries.
Cholesterol
A large body of evidence directly links serum cholesterol levels and CHD among women as well as men. Studies also show that low levels of high-density lipoprotein (HDL) cholesterol are the second most reliable predictor of CHD mortality (after age) among women (Jacobs, 1990). Women generally have lower cholesterol levels than men up to about age 50. After the menopause, however, levels of HDL, the ‘good’ cholesterol, fall and levels of LDL (low density lipoprotein), the ‘bad’ kind, rise. There is considerable evidence to indicate that lowering blood cholesterol levels leads to a decrease in CHD incidence among men. Evidence is also growing that lowering blood cholesteral levels can reduce the incidence of major heart attacks in women with heart disease and improve survival in older patients (Scandinavian Simvastatin Survival Study,1994). Guidelines on when and how to reduce cholesterol in healthy women have not yet been established except in cases of familial high cholesterol (Woods,1994).
Smoking
Smoking is thought to be responsible for neady half of all avoidable deaths, of which half are due to cardiovascular disease (Bartechi, 1994; MacKenzie, 1994). Women who smoke more than 40 cigarettes a day increase their risk of CHD 20-fold. Even light smokers (1-4 cigarettes a day) have more than twice the risk of coronary disease of nonsmokers (Willett, 1987). Within two years, women who give up may be able to decrease their risk of CHD mortality by about one-quarter (Kawachi, 1993). Research into the most effective ways to persuade women to stop smoking is important.
High blood pressure
There is a strong association between elevated blood pressure and CHD in women (Sigurdsson, 1984; Fiebach, 1989). The significant benefits of medication in the treatment of severe hypertension have been demonstrated for both men and women. On the other hand, long-term benefits of treating mild to moderate hypertension in women are no established, as women have only recently been included in clinical trials. Isolated systolic hypertension (an increase in the top, or systolic, blood pressure number) affects one in three women aged over 65. It signals a loss of arterial elasticity, which is associated with higher risk of stroke and CHD. Results from the Systolic Hypertension in the Elderly Program indicate that the incidence of stroke and heart attack is significantly lower in elderly patients treated for hypertension (SHEP Cooperative Research Group, 1991). Doctors, who customarily treat only the diastolic, or lower number, need to treat their older patients’ systolic hypertension too. This applies to men as well as to women.
Obesity
A number of large-scale prospective studies have begun to demonstrate associations between obesity and CHD in women as well as men. The largest of these, the Nurses’ Health Study, involving over 120,000 middle-aged American women, demonstrated that the risk of CHD was two or three times higher among women who are overweight, including those who are only moderately overweight. Other studies confirm that women who maintain their ideal body weight have a 35-60% lower risk of heart attack than those who exceed it (Manson, 1990).
Physical inactivity
Studies across the board support a strong link between physical inactivity and increased risk of CHD (Blair, 1994; 1996). Although most of the studies of the relationship between exercise and heart disease have been conducted on men (Powell 1987) evidence is mounting that physical inactivity is a strong risk factor for women too. An eight-year study of more than 3,000 healthy women correlated associations between physical fitness and reduced rates of mortality from CHD as well as other causes (Blair, 1989). Exercise is thought to reduce some of the known risk factors for CHD, such as cholesterol levels, high blood pressure and obesity. Exercise is as beneficial for women who exercise moderately as it is for those who are endurance-trained, which is good news from a public health perspective (Hardman, 1994).Unfortunately, the UK% 1990 National Fitness Survey found that more than eight out of 10 women undertook less than the minimum level of physical activity required for beneficial health results (Rhodes, 1994).
Hormonal changes
A traditional explanation for male-female differences in CHD is that classical risk factors, including cigarette smoking, high blood pressure and high blood cholesterol, are more common in men because of differences in lifestyles. This explanation, however, is not always convincing. Researchers have only recently begun to ask questions about the effects of female sex hormones on CHD. For example, pre-menopausal women are more likely to have lower blood pressure and cholesterol levels compared with men of the same age. The incidence of CHD in women increases dramatically in middle age, and there is growing evidence that the hormonal changes associated with the menopause contribute to older women’s risk. A classic study shows that women who had an early, surgically induced menopause and did not receive oestrogen replacement therapy had a 2.2 higher risk of CHD than that of pre-menopausal women of the same age (Colditz, 1987).
Oral contraceptives. The risk of CHD increases among women, particularly smokers, who used to take the high-dose oral contraceptives that are no longer commonly prescribed (Hennekens, 1979). Results of recent retrospective studies on today’s low-dose formulations of oral contraceptives suggest there is little or no increased risk for women currently in their 50s (Stampfer, 1990; Thorogood, 1993), and some studies even suggest a protective effect (Hirvonen, 1990).
Diabetes mellitus
This disorder is a stronger risk factor for CHD among women than among men. Mortality rates for diabetic women are three to seven times higher than for non diabetic women. Diabetic women also have more than a five-fold increase in their risk of stroke (Barrett-Connor, 1983; Manson, 1991).
Other factors
Alcohol. Results of a major study on the relationship between alcohol consumption and mortality in healthy women showed that light to moderate alcohol consumption (a beer, glass of wine or drink of spirits a day) was associated with a significantly reduced risk of death in women, due largely to a lower risk of fatal cardiovascular disease (Fuchs, 1995), paralleling findings for men. Heavier alcohol consumption was associated with increased mortality in women, due largely to an increased risk of death from other diseases, including breast cancer (Longnecker, 1994).
Stress. The psychosocial environment and a person’s ability to deal with stress also appear to have an impact on CHD risk (Theorell, 1992). It is often suggested, particularly in the popular press, that as more women move out of the home and into jobs traditionally regarded as ‘men’s jobs’, they will begin to experience increased stress and so increase their rates of CHD. Yet research indicates that economically deprived women in low paid, tedious employment and women who stay at home are just as likely to suffer from stress, if not more so, than career women.
Socio-economic factors. Studies show that women (and men, for that matter) in lower socioeconomic groups are more vulnerable to nearly all the classic risk factors (Marmot, 1991; Wenger, 1996).
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