Page 786 - Cardiac Nursing

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762 PA R T V / Health Promotion and Disease Prevention
women. 108 Weight gain after the young adult years increases the and venous thromboembolism. The risk of arterial and venous
risk of CHD in men and women. 86,100 In the Nurses Health thrombosis increases with the dosage of estrogen, whereas higher
Study, women who gained 20 to 35 kg after 18 years of age had dosages of progestogens increase only the risk of arterial throm-
double the risk of nonfatal MI and fatal CHD compared with bosis. 122,123 The second possible mechanism for the association
those who gained less than 3 kg. 86 between OCs and CHD risk is the promotion of atherogenesis
The role of the distribution of body weight has attracted in- through unfavorable effects on blood pressure, serum lipids, and
creasing attention. The primary hypothesis is that a central body glucose tolerance. 124
weight distribution, often measured as waist-to-hip ratio, in- Dosages of estrogen and progestin in current OCs are consid-
creases the CHD risk to a greater degree than a more peripheral erably lower than those of the 1970s, and there appears to be lit-
body weight distribution. Abdominal obesity, particularly waist tle or no risk of MI or CHD death among users of newer OC
circumference, has been strongly associated with development of formulations. 125–128 The exception is the finding in some 25,125
CVD in both men and women 109,110 and some have found waist but not all 126 studies of continued high risk among women who
circumference to be a better predictor of CVD risk than BMI. 111 are heavy cigarette smokers and OC users. A prospective cohort
In white men, abdominal girth was not associated with total or study in England and Scotland found a five-fold increase in the
CHD mortality, although black men in the 90th percentile for risk of MI among current smokers who used OCs. 125 It has been
abdominal girth had almost double the rate of CHD mortality estimated that 9.7% of cases of nonfatal MI among women aged
compared with those in the 50th percentile. 106 These results were 35 to 44 years in the United States are caused by the combination
reversed in women. There was no association between abdominal of smoking and OC use. 129 However, a U.S. case-control study of
circumference and all-cause or CHD mortality in black women, low-dose OCs and MI risk in women aged 18 to 44 years found
but white women in the 85th percentile of abdominal circumfer- no increase in the risk among smokers. 126 Another more recent
ence had a 50% increase in all-cause and CHD mortality com- study examined mortality from all causes and CVD deaths in re-
pared with those in the 15th percentile (see Chapter 38, for further lation to OC use during a 14-year follow-up among Norwegian
discussion of obesity). women who participated in a population-based health survey
from 1985 to 1988. 130 The study found that women using OC
of any type had no different adjusted total mortality (RR 0.87;
REPRODUCTIVE HORMONES 95% CI 0.46 to 1.65) or CVD mortality (RR 1.41; 95% CI 0.44
to 4.56) when compared with non-users. These findings support
previous research, which has indicated that neither CHD mor-
Reproductive History
tality nor overall mortality is increased with OC use. Overall,
Blood pressure and blood lipids change in relation to reproductive OCs appear to offer a safe contraceptive alternative in terms of
events. It is thus reasonable to investigate the potential impact of cardiovascular disease risk.
these events on the risk of CHD in women. Few studies have ex-
amined these factors, and their findings are contradictory. Nulli- Postmenopausal Hormone
parous women appear to be at lower risk of CHD than parous Replacement Therapy
women, and a woman’s risk of CHD may increase with younger
age at first birth. 26,112,113 Increasing parity may also increase The public health implications of HRT have shifted dramatically
CHD risk, perhaps because of the large changes in hormones as- with the publication of the findings from two landmark random-
sociated with pregnancy. 113 Others, however, have found no dif- ized, clinical trials: the Heart and Estrogen/Progestin Replace-
ferences in risk with parity and number of births. 114 ment Study (HERS) and the Women’s Health Initiative. Despite
Earlier age at menopause increases CHD risk regardless of the consistent findings of observational studies that HRT is asso-
the mechanism of menopause. Among women who undergo bi- ciated with a 30% to 50% reduction in CHD events in women
lateral oophorectomy, those younger than age 35 years have al- with 131 and without 116,132 preexisting CHD, the results of the
most eight times the risk for nonfatal MI compared with natural first randomized trial of the effects of HRT on the CHD risk
menopause. 115 Premenopausal women of any age who undergo bi- found no benefit. 133 The HERS study challenged our under-
lateral oophorectomy without estrogen replacement therapy have standing of the effects of HRT in women with cardiovascular
twice the risk of nonfatal MI and fatal CHD compared with pre- disease. There was a 50% increase in the relative risk of cardio-
menopausal women of the same age. 116 At menopause, serum vascular disease events in the first year of HRT use among
HDL levels decrease and LDL levels increase compared with pre- women with established coronary disease. Overall, there was no
menopausal values. 117,118 difference in the likelihood of cardiovascular events between
placebo and control. Because of the lack of overall benefit and
Oral Contraceptives the increased risk in the first year, the HERS investigators con-
cluded that women with coronary disease should not initiate
The increased risk for fatal and nonfatal MI in users of oral con- HRT.
traceptives (OCs) was first established in the 1960s and early The Women’s Health Initiative consisted of two parallel ran-
1970s. In these early studies, OC use was associated with an in- domized, double blind, placebo-controlled clinical trials of HRT
creased risk of nonfatal and fatal MI in young women. 119,120 which were designed to determine whether estrogen alone (for
Concurrent cigarette smoking acts synergistically with the risk women with prior hysterectomy) or estrogen plus progesterone
from OCs, with the greatest risk occurring in women who smoke would reduce CVD events in “mostly healthy” women. 134 The es-
and are older than age 35 years. 25,121 trogen plus progestin arm (planned duration 8.5 years) was
There are at least two mechanisms for the risk of cardiovascular stopped after an average of 5.2 years of follow-up because the
events associated with OCs. First, OCs increase the risk of arterial overall risks outweighed the benefits of therapy. 135 Compared to