Menopause and modifiable coronary heart disease risk factors: A population based study☆
Article Outline
Abstract
Objectives
The aim of our study was to determine the effect of the menopause on various coronary heart disease (CHD) risk factors and on the global risk of CHD in a population based sample of women, making the difference between menopause and age related effects.
Study design
The Third French MONICA cross-sectional survey on cardiovascular risk included 1730 randomly selected women, aged 35–64 years, representative from the general population.
Main outcome measures
Women were defined as post-menopausal (postM; n
=696), peri-menopausal (periM; n=183) or pre-menopausal (preM; n=659) based on the date of last menses. Socio-demographic, clinical and biological data were collected. Analyses of variance were used to compare means.
Results
PostM women had significantly higher age-adjusted levels of total cholesterol (6.0mmol/L in postM vs. 5.7mmol/L in preM, p<0.05) and LDL cholesterol (3.9mmol/L vs. 3.6mmol/L, p<0.05). There was no difference in HDL cholesterol or triglyceride levels, glycemia or blood pressure. Further adjustment on body mass index and hormonal treatments did not modify the results. No risk factor was significantly different between periM and postM. However, the Framingham 10-year risk of CHD was higher in postM, as compared with periM (5.1% vs. 5.0%, p<0.05). In postM women, lipids and the Framingham risk were not associated with elapsed time since menopause.
Conclusions
The CHD risk increases during the sixth decade could be explained not only by estrogen deprivation but also by an effect on lipid profile, which is likely to occur in the peri-menopause period.
Keywords: Coronary heart disease risk factors, Menopause, Lipids, Epidemiology
1. Introduction
Coronary heart disease (CHD) mortality in women increases after the sixth decade of life [1]. Most women become menopausal during this age range. The increase in CHD risk could be directly due to oestrogen deprivation, or indirectly due to an increase of CHD risk factor prevalence, such as dyslipidemia, diabetes mellitus, overweight, or hypertension at the time of menopause. Several cross-sectional studies have shown high total cholesterol level [2], [3], [4], high LDL cholesterol level [3], [4] and high triglyceride level [2], [3], [4] associated with menopausal status. Longitudinal studies also showed increased total cholesterol level [5], [6], [7], increased LDL cholesterol level [5], [6], [7], or increased serum triglyceride level [6], [7] at the time of menopause. Some of these studies enrolled population based samples of women from the United States [3], [7] or from Northern Europe [6]. But as far as we knew, there was no population based study on the association between menopausal status and CHD risk factors in countries with low CHD incidence or mortality, such as the Southern European area [8], [9]. The prevalence of CHD risk factors such as body mass index, or systolic blood pressure differ in Southern Europe [10]. Lower mean serum cholesterol has been reported in Southern Europe compared to Northern Europe or the United States [8]. Different fatty acid proportions in diet [11] or other nutrients [1] could also modify the occurrence of CHD in this area. Furthermore, from a clinical practice point of view, the most commonly used hormone replacement regimen is transdermal 17β-estradiol associated with progestin in these countries [12]. Thus, studies of the effect of menopause on CHD risk factors which focus on a Southern European country-sized population based sample are needed.
The objective of this study was to determinate the impact of the menopausal status on various CHD risk factors in a sample of French women, making the difference between menopause related effects and age related effects.
2. Methods
2.1. Design
Our study included every woman who participated in the Third French MONICA cross-sectional survey on cardiovascular risk factors. The aim of the MONICA (MONItoring of trends and determinants in CArdiovascular disease) Project has already been extensively described elsewhere [13].
Briefly, the Third French MONICA cross-sectional Survey on CHD risk factors was carried out between December 1994 and July 1997. An institutional review committee in agreement with the French law on human biomedical research approved it. A population based sample of middle-aged men and women (35–64 years) living in the Toulouse area (South-western France), Lille area (North France), and Bas-Rhin area (East France) was randomly recruited. Polling lists available in each town hall of the survey areas were used for sampling in order to carry out a random selection of the general population. The informed consent to participate in the study was obtained from each subject before the beginning of the survey. The participation rate was 66%.
2.2. Data collection
Extensive questionnaires were filled out during guided interview by a trained and certified medical staff. Data concerning socio-economic level, medical history, personal history of menacme events, drug intake, CHD risk factors, and life style were recorded. Height, weight and arterial blood pressure (mean of two measurements performed with a standard sphygmomanometer in a sitting position after a 5-min rest at least) were measured according to standardised protocols by the medical staff. Body mass index was calculated as weight divided by height squared (kg/m2). Blood samples were taken after at least 10h of overnight fasting. Serum glucose, total cholesterol, high-density lipoprotein (HDL) cholesterol, A1 Apolipoprotein (Apo A1), B Apolipoprotein (Apo B) and triglyceride concentrations were measured. Low density lipoprotein (LDL) cholesterol was determined by Friedewald formula [14]. Framingham 10-year risk of CHD was also determined [15].
Women were allocated to the pre-menopausal group (NM), the peri-menopausal group (PM), or the post-menopausal group (M) according to an algorithm derived from the diagram used in the Women's Ischemia Syndrome Evaluation (WISE) study to determine the reproductive hormone status. This diagram has been previously described [16]. As shown in Fig. 1, an amenorrhea for at least 12 months defined the menopausal status of the women. Among the 1730 women of the initial sample, 40% were post-menopausal, 11% had a personal history of hysterectomy, 11% were peri-menopausal and 38% were pre-menopausal. Unavailable data on the regularity of their menstrual cycles or on ovarian preservation for the women who had a hysterectomy constrained us to exclude 192 women out of the initial sample.
Fig. 1.
Distribution of the women according to their menopausal status.
In the post-menopausal group, elapsed time since menopause, i.e. the elapsed time between the date of the last menstruation and the date of the survey, was available for 97% of the women.
Lipid-lowering therapy, diabetes mellitus, antihypertensive and hormonal treatments were considered as potential confounding factors. Lipid-lowering therapy was defined as the daily intake within the last 15 days of at least one lipid-lowering drug among those defined by the National Guide Drug Prescription [17] used at the time of the study. Similar definitions of treatments were used for diabetes mellitus and antihypertensive treatments. Hormonal treatments were defined by the daily intake of contraceptive drugs or hormone replacement therapy [17].
2.3. Statistical analyses
Statistical analyses were performed using STATA 9.0 statistical software (Stata Corporation, College Station, TX, USA). When p<0.05, it was considered as statistically significant.
The Chi-square test was used to compare the percentages.
The analysis of variance (ANOVA) was used to compare means. The distributions of the serum triglyceride level, the body mass index, and the 10-year Framingham risk of CHD were skewed. Thus, serum triglyceride level and the 10-year Framingham risk of CHD were log transformed, and body mass index was inversed transformed in statistical tests in order to fulfil the condition of normality when required. The Bartlett test for homoscedasticity was used. A variance ratio of 1:2 between groups was tolerated since the ANOVA remains robust to that ratio of variance heterogeneity [18].
The analysis of factors associated with CHD risk factors was conducted with analysis of covariance (ANCOVA). Age at the time of the study, body mass index, lipid and blood pressure lowering therapies, antidiabetic and hormonal treatments were considered as potential confounding factors.
For multiple comparisons, Holm correction [19] was used to maintain the global alpha risk at the level of 0.05.
To assess the linearity of CHD risk factors across the 4 quartiles of elapsed time since menopause, the fractional polynomial method was used [20].
3. Results
3.1. Characteristics of the sample
The mean age of the whole sample was 50.3 (SD 8.5) years. Most of the women were employees (45%), had a low physical activity (52%), and never smoked cigarettes (65%). The prevalence of family history of CHD was 26% (Table 1).
Table 1. Description of the life style and the CHD risk factors.
| All n=1730 %[95%CI] | Pre-menopausal n=659 n (%) | Peri-menopausal n=183 n (%) | Post-menopausal n=696 n (%) | Unadjusted p-value | |
|---|---|---|---|---|---|
| Occupational categories | – | ||||
| Farmers | 2.0 [1.4–2.8] | 4 (0.6) | 2 (1.1) | 25 (3.6) | |
| Craftswomen, saleswomen, managers | 5.3 [4.3–6.5] | 17 (2.6) | 5 (2.7) | 57 (8.2) | |
| Senior executive professionals | 8.4 [7.1–9.8] | 71 (10.8) | 17 (9.3) | 38 (5.5) | |
| Middle executive professionals | 23.1 [21.1–25.1] | 172 (26.1) | 54 (29.5) | 140 (20.1) | |
| Employees | 45.0 [42.6–47.4] | 303 (46.1) | 76 (41.5) | 313 (45.0) | |
| Workers | 13.2 [11.6–14.9] | 79 (12.1) | 24 (13.1) | 93 (13.4) | |
| Housewives | 3.0 [2.3–3.9] | 12 (1.8) | 5 (2.7) | 29 (4.2) | |
| Physical activity | 0.006 | ||||
| None | 27.0 [24.9–29.1] | 172 (26.1) | 47 (25.7) | 185 (26.6) | |
| Low | 51.9 [49.6–54.3] | 317 (48.1) | 94 (51.4) | 385 (55.7) | |
| Moderate | 14.0 [12.4–15.7] | 119 (18.1) | 31 (16.9) | 74 (10.7) | |
| High | 7.1 [5.9–8.4] | 51 (7.7) | 11 (6.0) | 49 (7.1) | |
| Smoking status | <0.001 | ||||
| Never | 65.2 [62.8–67.4] | 355 (53.9) | 106 (57.9) | 522 (75.0) | |
| Ever | 17.5 [15.8–19.4] | 143 (21.7) | 33 (18.0) | 99 (14.2) | |
| Current <10 cig. per day | 6.4 [5.3–7.7] | 57 (8.6) | 21 (11.5) | 28 (4.0) | |
| Current ≥10 cig. per day | 10.9 [9.5–12.5] | 104 (15.8) | 23 (12.6) | 47 (6.8) | |
| Family history of CHD | 26.3 [24.2–28.4] | 150 (22.8) | 44 (24.0) | 206 (29.6) | 0.013 |
| All n=1730 Mean (SD) | Pre-menopausal n=659 Mean (SD) | Peri-menopausal n=183 Mean (SD) | Post-menopausal n=696 Mean (SD) | Unadjusted p-value | |
|---|---|---|---|---|---|
| Age (yrs) | 50.9 (8.5) | 42.8 (4.4) | 49.1 (4.4) | 57.4 (5.4) | <0.001 |
| Body mass index (kg/m2) | 25.9 (5.3) | 24.8 (4.9) | 25.3 (5.2) | 26.7 (5.2) | <0.001 |
| Waist circumference (cm) | 84.5 (13.8) | 80.5 (12.7) | 83.2 (14.0) | 87.4 (13.2) | <0.001 |
| Systolic blood pressure (mmHg) | 129 (20) | 121 (16) | 126 (17) | 136 (20) | <0.001 |
| Diastolic blood pressure (mmHg) | 80 (11) | 77 (11) | 79 (10) | 82 (11) | <0.001 |
| Fasting glycemia (mmol/L) | 5.4 (1.4) | 5.2 (1.4) | 5.3 (1.1) | 5.5 (1.4) | <0.001 |
| Serum lipids | |||||
| Total cholesterol (mmol/L) | 5.9 (1.1) | 5.4 (0.9) | 5.8 (1.0) | 6.2 (1.1) | <0.001 |
| LDL cholesterol (mmol/L) | 3.7 (1.0) | 3.4 (0.9) | 3.7 (1.0) | 4.0 (1.0) | <0.001 |
| HDL cholesterol (mmol/L) | 1.7 (0.5) | 1.6 (0.4) | 1.7 (0.5) | 1.7 (0.5) | 0.002 |
| Triglycerides (mmol/L) | 1.1 (1.1) | 1.0 (0.6) | 1.1 (0.9) | 1.2 (1.4) | <0.001 |
| Apolipoprotein A-1 (g/L) | 1.8 (0.3) | 1.7 (0.3) | 1.8 (0.3) | 1.8 (0.3) | <0.001 |
| Apolipoprotein B (g/L) | 1.2 (0.3) | 1.1 (0.2) | 1.1 (0.3) | 1.2 (0.3) | <0.001 |
| Framingham score (% 10 yrs) | 5.3 (5.2) | 2.3 (2.8) | 4.5 (4.1) | 7.7 (5.5) | <0.001 |
For the post-menopausal women, the mean elapsed time since menopause was 8.5 (SD 5.8) years.
Among the 1730 women, 15.0% (CI95% [13.3–16.7]) were taking daily antihypertensive drugs, 3.7% (CI95% [2.9–4.7]) were taking daily diabetes mellitus treatment, and
11.5% (CI95% [10.0–13.1]) were taking daily lipid-lowering therapy. The prevalence of those treatment intakes was not associated with menopausal status after adjustment for age (Table 2). Within the 328 women currently taking hormonal replacement therapy, the prevalence of the use of transdermal 17β-estradiol was 64.6% (CI95% [59.2–69.8]).
Table 2. Description of drug intake according to menopausal status.
| Pre-menopausal n=659 n (%) | Peri-menopausal n=183 n (%) | Post-menopausal n=696 n (%) | Unadjusted p-value | Age-adjusted p-value | |
|---|---|---|---|---|---|
| Hormonal treatment | |||||
| Hormone replacement therapy | 48 (7.3) | 19 (10.4) | 208 (29.9) | <0.001 | <0.001 |
| Oral contraceptives | 105 (15.9) | 7 (3.8) | 3 (0.4) | <0.001 | <0.001 |
| Blood pressure lowering therapy | 38 (5.8) | 18 (9.8) | 202 (22.8) | <0.001 | ns |
| Diabetes treatments | 14 (2.1) | 5 (2.7) | 35 (5.0) | 0.012 | ns |
| Lipid-lowering therapy | 16 (2.4) | 12 (6.6) | 134 (19.3) | <0.001 | ns |
3.2. CHD risk factors according to menopausal status
Body mass index, waist circumference, blood pressure, glycemia, serum lipid profile, Framingham 10-year risk of CHD means were associated with the menopausal status (Table 1).
Body mass index, blood pressure, fasting glycemia, triglyceride, serum HDL cholesterol and apolipoprotein A1 levels did not differ according to menopausal status after adjustment for age. Whereas serum total cholesterol, LDL cholesterol and the Framingham 10-year risk of CHD were higher in the post-menopausal women. Further adjustment for BMI and treatments did not change the results (Table 3). Nor did further adjustments for physical activity, smoking habits, and fasting blood glucose.
Table 3. Comparison of age-adjusted means of CHD risk factors according to menopausal status.
| Pre-menopausal n=659 Mean (SD) | Peri-menopausal n=183 Mean (SD) | Post-menopausal n=696 Mean (SD) | Age-adjusted p-value | Age and BMI adjusted p-value | Age, BMI and treatment adjusted p-value | |
|---|---|---|---|---|---|---|
| Body mass index (kg/m2) | 25.7 (7.1) | 25.7 (1.7) | 25.8 (7.0) | ns | – | – |
| Systolic blood pressure (mmHg) | 129 (25) | 129 (6) | 128 (24) | ns | ns | ns |
| Diastolic blood pressure (mmHg) | 79 (16) | 80 (4) | 80 (15) | ns | ns | ns |
| Fasting glycemia (mmol/L) | 5.4 (1.9) | 5.3 (0.5) | 5.3 (1.8) | ns | ns | ns |
| Serum lipids | ||||||
| Total cholesterol (mmol/L) | 5.7 (1.4) | 5.8 (0.3) | 6.0 (1.4) | (i), (ii) | (i), (ii) | (i), (ii) |
| LDL cholesterol (mmol/L) | 3.6 (1.3) | 3.7 (0.3) | 3.9 (1.3) | (ii) | (ii) | (i), (ii) |
| HDL cholesterol (mmol/L) | 1.6 (0.6) | 1.7 (0.2) | 1.7 (0.6) | ns | ns | ns |
| Triglycerides (mmol/L) | 1.0 (1.5) | 1.1 (0.4) | 1.2 (1.5) | ns | ns | ns |
| Apolipoprotein A-1 (g/L) | 1.8 (0.4) | 1.8 (0.1) | 1.8 (0.4) | ns | ns | ns |
| Apolipoprotein B (g/L) | 1.1 (0.4) | 1.1 (0.1) | 1.2 (0.4) | (ii) | ns | (ii) |
| Framingham score (% 10 years) | 5.0 (5.6) | 5.0 (1.4) | 5.1 (5.5) | (i) | (i), (iii) | (i), (iii) |
3.3. CHD risk factors according to elapsed time since menopause (Table 4)
Body mass index, systolic blood pressure and the Framingham 10-year risk of CHD means had a linear trend to increase across the four quartiles of elapsed time since menopause, whereas elapsed time since menopause had no impact on lipid profile.
Table 4. Coronary heart disease risk factor according to quartiles of elapsed time since menopause.
| Quartiles [Min–Max] (years) | Quartile 1 [0.6–4.3] n=188 Mean (SD) | Quartile 2 [4.3–8.3] n=184 Mean (SD) | Quartile 3 [8.3–13.2] n=170 Mean (SD) | Quartile 4 [13.3–42.1] n=135 Mean (SD) | Unadjusted p-value | Age-adjusted p-value | Age, BMI and treatment adjusted p-value |
|---|---|---|---|---|---|---|---|
| CHD risk factors | |||||||
| Age (years) | 53.4 (4.0) | 56.0 (4.9) | 60.6 (3.6) | 62.6 (3.2) | <0.001 | – | – |
| Body mass index (kg/m2) | 26.1 (4.9) | 26.5 (5.3) | 26.8 (4.6) | 27.7 (6.0) | 0.049 | ns | ns |
| Systolic blood pressure (mmHg) | 132 (19) | 135 (19) | 138 (21) | 143 (22) | <0.001 | ns | ns |
| Diastolic blood pressure (mmHg) | 81 (11) | 82 (10) | 82 (12) | 84 (12) | ns | ns | ns |
| Fasting glycemia (mmol/L) | 5.5 (1.7) | 5.4 (1.2) | 5.5 (1.0) | 5.6 (1.5) | ns | ns | ns |
| Serum lipids | |||||||
| Total cholesterol (mmol/L) | 6.2 (1.1) | 6.2 (1.1) | 6.3 (1.0) | 6.3 (1.0) | ns | ns | ns |
| LDL cholesterol (mmol/L) | 4.0 (1.0) | 4.0 (1.1) | 4.1 (1.0) | 4.1 (1.0) | ns | ns | ns |
| HDL cholesterol (mmol/L) | 1.7 (0.5) | 1.7 (0.5) | 1.6 (0.5) | 1.7 (0.5) | ns | ns | ns |
| Triglycerides (mmol/L) | 1.3 (2.6) | 1.1 (0.7) | 1.2 (0.6) | 1.2 (0.5) | ns | ns | ns |
| Apolipoprotein A-1 (g/L) | 1.8 (0.3) | 1.8 (0.3) | 1.8 (0.3) | 1.9 (0.3) | ns | ns | ns |
| Apolipoprotein B (g/L) | 1.2 (0.3) | 1.2 (0.3) | 1.2 (0.3) | 1.3 (0.3) | ns | ns | ns |
| Framingham score (% 10 years) | 6.0 (4.2) | 7.2 (5.5) | 8.7 (5.5) | 9.6 (6.1) | <0.001 | ns | ns |
Body mass index, systolic blood pressure and the Framingham 10-year risk of CHD were no more associated with elapsed time since menopause after adjustment for age. Further adjustment for body mass index and treatments did not modify these results.
4. Discussion
Serum total cholesterol and LDL cholesterol levels and the Framingham 10-year risk of CHD remained higher in the post-menopausal group after adjustment for age, body mass index and treatments. But the lipid profile and the Framingham 10-year risk of CHD were not associated with elapsed time since menopause.
4.1. Changes in lipid profile
Since the end of the 1980s, we know that the relationship between serum total cholesterol level and coronary heart disease death rate is continuously graded [21]. Furthermore, in a population with low serum cholesterol levels, Chen et al. showed that a 10% difference in baseline serum cholesterol concentration (that is, a difference of 0.41mmol/L) was independently associated with a 21% excess risk of death from coronary heart disease in Cox regression models adjusted for age, sex, diastolic blood pressure, cigarette smoking and alcohol drinking [22]. A 0.3mmol/L age-adjusted increase in serum total cholesterol level between the pre-menopausal and the post-menopausal groups not only reached statistical significance in our analyses, but was also clinically relevant.
These higher lipid levels in the post-menopausal group are consistent with those of other cross-sectional studies. Higher serum total cholesterol levels [3], [23] or higher serum LDL cholesterol levels [3], [23] in the post-menopausal women have been previously described at a population level in the Northern America or in the Northern Europe. As the CHD mortality [8], [9], the prevalence of CHD risk factors [8], [10], the life style, the diet habits [1], [11], and the clinical practice concerning hormone replacement therapy [12] differs in France, the study of the relationship between the coronary heart disease risk factors and menopausal status in those population was needed. French women of two health care centres have been studied [2], [4], and one population based study described changes in total cholesterol and LDL cholesterol levels [24] in a city of the Northern Italy, involving 329 of the women of the Virgilio Menopause Health Project, with a proportion of women included in the analysis reaching 74% of the women who participated in the study. In French women, changes in serum total cholesterol and LDL cholesterol are associated with the menopausal status independently of age, BMI, and treatments.
Furthermore, there was no relationship between CHD risk factors and elapsed time since menopause in the post-menopausal group after adjustment for age. The cross-sectional design of our study does not allow us to draw firm conclusions about the chronology of the events. However, the fact that no relationship between elapsed time since menopause and lipid levels and no differences of age-adjusted lipid level means between the peri- and the post-menopausal groups were found suggest that the changes in lipid profile should occur in the peri-menopause period. Those results are consistent with the ones of previous longitudinal studies about the menopause impact on the lipids in Northern American [7], Northern European [6], Chinese [25], and Japanese [5], [26] population based samples of women.
The observed lipid changes could be explained by serum estrogen level decrease at the time of the menopause. Actually, the post-menopausal use of oral estrogens in low doses favourably alters LDL and HDL levels that may protect women against atherosclerosis [27]. Estrogens induce an early increase of LDL receptors, which are responsible for the uptake of plasma lipoproteins, and decrease 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR) activity [28], which is the key enzyme of the biosynthetic pathway. Moreover, estrogens enhance biliary secretion of cholesterol [29]. All these results suggest that estrogens may contribute to decrease serum LDL cholesterol levels. Conversely, estrogen plasma level decrease observed at the time of the menopause may result in a serum LDL cholesterol increase.
4.2. The Framingham 10-year risk of CHD
The Framingham coronary 10-year risk score performs well in various American populations [30], but this score is known to overestimate the risk of CHD in Europe [31], particularly in the Southern European Countries [32]. In our study the Framingham predictive 10-year risk of CHD was used to assess the global risk of CHD among women. The overestimation is unlikely to have biased the estimated risk comparison between the pre-menopausal and the post-menopausal groups if this bias was not differential. However, the difference between the Framingham predicted and observed absolute CHD risk increases with age [33]. To avoid the age confounding effect on the relationship between the Framingham predicted 10-year risk of CHD and the menopausal status, we adjusted for age. After further adjustment for other potential confounding factors such as BMI or treatments, the predicted risk of CHD was still higher in the post-menopausal women. Therefore, the changes in lipid profile should have a significant impact on the global risk of CHD for women at the time of the menopause.
4.3. Hormone replacement therapy
The beneficial effects of the hormone replacement therapy (HRT) on lipid profile are well documented [34]. Several clinical trials on hormone replacement therapy have been conducted. The results from the post-menopausal Estrogen Progestin Interventions (PEPI) corroborate the conclusions about improved lipid profile in the HRT group [35]. The inconclusive results from the Heart and Estrogen/progestin Replacement Study (HERS) [36] or the increased CHD events’ rate from the Women's Health Initiative (WHI) [37] in the HRT group were conflicting with the PEPI trial results. A scientific review rose the attention on the post-menopausal HRT harming effect on the occurrence of CHD events [38]. All those results considerably modified the French guidelines for the prescription of the HRT in the decade following our survey [39]. Ten years earlier, at the time of our survey, physicians were likely to refer to results of the observational studies [40], which supported HRT use for their clinical practice. This could explain the huge rate of women with HRT daily intake in the post-menopausal group in our study.
The characteristics of the women using HRT differ from those of the non-users. Actually, for example, estrogen users tend to have greater contact with the health care system [34]. Therefore, the exclusion of the HRT users would have led us to a major selection bias, whereas one of the strength of our study was to allow us to draw conclusions at a population level. Thus, the HRT use had been considered as a confounding factor in the analysis to take into account this healthier HRT user effect.
4.4. Limitations of the study
The cross-sectional design did not allow us to draw firm conclusions about the chronology of the observed lipid changes, but our results suggest that the lipid profile could be modified in the peri-menopause period, and that these changes are independent from age, lipid-lowering therapy and hormonal therapies.
Women were considered as treated by lipid or blood pressure lowering therapies or by antidiabetic treatments or by hormonal therapy if a description of the drug prescription was provided. Some of the women were likely to have lost or forgotten their drug prescription at the time of the assessment. Thus, the proportion of treated women could have been underestimated. Another way to estimate the proportion of treated women was to consider as treated the women who declared daily drug intake in the past 2 weeks without further details. This estimation would have been likely to overestimate the percentages of treated women. The use of the latest definition of the treated women in our analysis did not modify our results.
At the time of the study, some physicians already prescribed lipid-lowering therapy as further recommended in the French guidelines published in 1996 [41]. The decreasing LDL cholesterol threshold to start lipid-lowering therapy with age could have explained the relative stability of lipid profile with elapsed time since menopause. Thus, lipid-lowering therapy adjustments were conducted in the analysis.
The reproductive hormone status diagram of the Women's Ischemia Syndrome Evaluation (WISE) study [16] was based on the personal history of hysterectomy and oophorectomy, a threshold age of 55 years, the regularity of menstrual bleedings, and blood determinations of reproductive hormones. Data concerning the personal history of bilateral oophorectomy was not available in our study. The uncertainty of the ovarian preservation for the women who underwent hysterectomy might have biased the results if those women were arbitrarily included as post-menopausal. Thus, women with a personal history of hysterectomy (n=190) were excluded. The resulting selection bias was unlikely to change the relationship between lipid levels and the menopausal status. Actually, analyses of the whole women sample (n=1730) – results not presented – considering women with a personal history of hysterectomy as post-menopausal women, did not change our results. Since data on reproductive hormone plasmatic levels were not available, a lower threshold age of 40 years was chosen to make the difference within the non-menopausal women between the peri-menopausal women and the pre-menopausal women (Fig. 1).
Last, the differences in social and occupational category, smoking habits, or in physical activity level observed could be explained by a generation effect. And this effect could also explain a part of the differences observed in lipid profile according to menopausal status. Unfortunately, our available data did not allow us to take this effect into account.
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☆ This paper has been previously presented as moderated poster in European Society of Cardiology Congress, September 2007, Vienna (Austria); as poster in Congrès de la Nouvelle Société Française d’Athérosclérose, Juin 2007, Biarritz (France).
PII: S0378-5122(09)00448-4
doi:10.1016/j.maturitas.2009.11.023
© 2009 Elsevier Ireland Ltd. All rights reserved.
