Sex differences in risk factors for coronary heart disease: a study in a Brazilian population

Abstract

In Brazil coronary heart disease (CHD) constitutes the most important cause of death in both sexes in all the regions of the country and interestingly, the difference between the sexes in the CHD mortality rates is one of the smallest in the world because of high rates among women. Since a question has been raised about whether or how the incidence of several CHD risk factors differs between the sexes in Brazil the prevalence of various risk factors for CHD such as high blood cholesterol, diabetes mellitus, hypertension, obesity, sedentary lifestyle and cigarette smoking was compared between the sexes in a Brazilian population; also the relationships between blood cholesterol and the other risk factors were evaluated. The population presented high frequencies of all the risk factors evaluated. High blood cholesterol (CHOL) and hypertension were more prevalent among women as compared to men. Hypertension, diabetes and smoking showed equal or higher prevalence in women in pre-menopausal ages as compared to men. Obesity and physical inactivity were equally prevalent in both sexes respectively in the postmenopausal age group and at all ages. CHOL was associated with BMI, sex, age, hypertension and physical inactivity. In this population the high prevalence of the CHD risk factors indicated that there is an urgent need for its control; the higher or equal prevalences of several risk factors in women could in part explain the high rates of mortality from CHD in females as compared to males.

Background

In Brazil coronary heart disease (CHD) constitutes the most important cause of death in both sexes in all the regions of the country and interestingly, the difference between the sexes in the CHD mortality rates is one of the smallest in the world because of high rates among women. Since a question has been raised about whether or how the incidence of several CHD risk factors differs between the sexes in Brazil the prevalence of various risk factors for CHD such as high blood cholesterol, diabetes mellitus, hypertension, obesity, sedentary lifestyle and cigarette smoking was compared between the sexes in a Brazilian population; also the relationships between blood cholesterol and the other risk factors were evaluated.

Results

The population presented high frequencies of all the risk factors evaluated. High blood cholesterol (CHOL) and hypertension were more prevalent among women as compared to men. Hypertension, diabetes and smoking showed equal or higher prevalence in women in pre-menopausal ages as compared to men. Obesity and physical inactivity were equally prevalent in both sexes respectively in the postmenopausal age group and at all ages. CHOL was associated with BMI, sex, age, hypertension and physical inactivity.

Conclusions

In this population the high prevalence of the CHD risk factors indicated that there is an urgent need for its control; the higher or equal prevalences of several risk factors in women could in part explain the high rates of mortality from CHD in females as compared to males.

Background

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] and now CHD constitutes the most important cause of death in both sexes and in all the regions of the country.

]. Since a question has been raised about whether or how the incidence of several CHD risk factors differs between the sexes in Brazil, we evaluated data on the occurrence of these risk factors in a population from the city of Campinas, State of São Paulo. We also measured the influence of the CHD risk factors on blood cholesterol.

Materials and Methods

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]. In this case, since we have three levels of cholesterol, a proportional odds model was used in the logistic regression.

Results

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Blood cholesterol and anthropometric data among men and women and in the total population. Data presented as mean ±SD, interval, (n = number of subjects)

: p = 0.005

). This sex difference was found in the CHD risk age groups: 5.75 ± 1.14 (age ≥ 55 y, women) versus 5.23 ± 1.19 mmol/L (age ≥ 45 y, men, "t" test, p = 0.001). There was no difference in the younger age groups: 4.66 ± 1.09 (age 20-54 y, women) versus 4.64 ± 1.11 mmol/L (age 20-44 y, men, "t" test, p = 0.630). Postmenopausal women presented higher CHOL levels when compared with younger women: 5.75 ± 1.14 versus 4.66 ± 1.09 mmol/L (p = 0.001) and in men CHOL also increased with age: 5.23 ± 1.19 versus 4.64 ± 1.11 mmol/L (p = 0.001) as expected.

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Percentage distribution of different levels of total blood cholesterol between the sexes by age

p = 0.001

, obesity (44%) and sedentary lifestyle (48%) were the most common risk factors in this population and diabetes the least common (4%, as expected), but the data do not differ from those found in developed countries. Hypertension and smoking habit had practically the same frequencies around 20%. Among men, in decreasing order of frequencies, the data showed: obesity, sedentary lifestyle, smoking, hypertension and diabetes. Among women, however, the decreasing sequence was different: sedentary lifestyle, obesity, hypertension, smoking and diabetes.

Prevalence (%) of risk factors for coronary heart disease among men and women and in the total population

p = 0.029 DM-diabetes; HY- hypertension; OBES- obesity; SEDEN- physical inactivity; SMOK- smoking

The comparison between the sexes showed that there were significant statistical differences in the frequencies of hypertension (1.4 times higher in women), obesity and smoking (respectively 1.2 and 1.3 times higher in men). Physical inactivity, the most frequent risk factor in this population, and diabetes were similar in the sexes.

shows age distribution of risk factors in both sexes. Diabetes was not present in younger men. Its prevalence did not differ between the group ages in women. In the older groups, no differences were found between the sexes. Women presented higher frequencies of hypertension than men did in both age groups, indeed twice as high in the younger group (8X18%). In both sexes the prevalence of hypertension was 2 to 3.5 times higher in the older ages as compared to the younger. The distribution of obesity between the age groups was not different in men, but in women the frequency was higher in older ages. In men the prevalence was higher than in women only in the younger group and no differences were found among the older groups. Physical inactivity was the only risk factor similar between the sexes in both age groups and equally frequent in the two age groups. The higher prevalence of smoking in men was found only in the older group. It was high in the younger groups and there were no differences between the sexes in those age groups (29 versus 26%). Younger women smoked 4 times more than the older ones and younger men 1.6 times more.

Prevalence (%) of risk factors for coronary heart disease according to sex and age

p = 0.020; fxm = 0.019 DM-diabetes; HY-hypertension; OBES-obesity; SEDEN-physical inactivity; SMOK-smoking

the same associations between variables for the cut off age of 50 y are shown.

Influence of coronary heart disease risk factors on blood cholesterol in the total population

= confidence interval

Influence of coronary heart disease risk factors on blood cholesterol by age

= confidence interval

summarizes the changes of prevalence of CHOL above 6.22 mmol/L according to sex, age (all ages up to 80 y) and BMI.

Probability of CHOL > 6.22 mmol/dL by age, sex and BMI.

Discussion

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) were more prevalent among women as compared to men. High CHOL was present in the sub-population of women in the postmenopausal age, as expected, but pre-menopausal women in this population presented equal levels of CHOL when compared to men suggesting an additional risk at pre-menopausal ages.

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] but hypertension was also two times higher in younger women as compared to men from ages 20 to 44 y. Again, younger women in this population are more exposed to this major risk factor.

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Men presented a higher prevalence of obesity than women did only in the younger group, but there were no differences in the older age groups. The prevalence increased with age only in women aggregating another risk factor to the postmenopausal period.

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). There were no differences between the sexes in the younger age groups leading to another undesirable risk at younger ages in women.

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], hypertension and physical inactivity were the risk factors that influenced CHOL. Since sex and age are not modifiable, the control of obesity should be seriously implemented in Brazil.

]) for either overweight and obese individuals or not. The higher BMI is associated with a higher prevalence of CHOL.

, in women at and above 50 y the risk of having CHOL >6.22 mmol/L was 2 times higher than for men; before 50 y men had a 20% higher chance than women; at and above age 50 y the chance of high CHOL for BMI<25 is 1.02 as compared to BMI ≥ 25; below 50 y the chance of high CHOL for BMI ≥ 25 is 1.8 higher than for BMI below 25, showing that factors related to obesity are much less influential in older ages, a period when the interaction age/sex predominated.

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Pre-publication history

The pre-publication history for this paper can be accessed here:

Acknowledgements

We thank Merck Sharp & Dohme, Brazil, for their technical support to carry out this study.