21 March, 2016:
Paula and colleagues in 2013 conducted a cross-sectional study to investigate the association between smoking and early onset of menopause . The study included 1222 female employees on the campuses of Rio de Janeiro university. All participants were aged over 35 years. Smoking status was determined by questioning whether the participant had smoked at least 100 cigarettes during her lifetime, and whether she currently smoked. Women were classified as current smokers, former smokers or women who had never smoked. The researchers used a Cox proportional hazards model to investigate the data and the correlations between smoking status and age at the onset of menopause.
Among current smokers, there was an increase of 56% (hazard ratio 1.56; 95% confidence interval 1.06-2.31) in the risk of menopause, when compared with those who had never smoked (p = 0.02), while former smoking was not associated with the outcome. The results obtained from the study revealed that women who smoke are 1.8 years younger at the onset of menopause when compared to non-smoking women. There was no significant difference between the survival curves for former smokers and women who had never smoked, adding a very interesting conclusion: once a woman gives up smoking, her age at onset of menopause may be roughly equivalent to that of women who have never smoked. The results obtained from the study emphasize the importance of efforts to control cigarette smoking.
Menopause is defined as a physical change experienced by women when going through the aging process . A harmful association between younger age at menopause and overall mortality has been recently documented, despite the results of Bernard, who investigated the correlation between smoking and early menopause among American women in 1949, and revealed a negative correlation .
Many authors have claimed that there are many factors on which the age at natural menopause (ANM) depends, such as genetic, socioeconomic, environmental, reproductive, dietary, and lifestyle factors. Some of these factors are have been proven to accelerate the ANM, like smoking, high fat intake, cholesterol, and caffeine, while other factors delay the ANM, such as parity, prior use of oral contraceptive pills and Japanese ethnicity. ANM is an important risk factor for mortality and long-term morbidity, and hence, we need to identify the modifiable risk factors and lifestyle changes .
In 2007, a substudy of 2123 postmenopausal women, who were born in 1940–41 and who had participated in the cross-sectional Oslo Health Study, was made to examine the association between early menopause and selected lifestyle factors. The authors defined early menopause as menopause occurring at an age less than 45 years. The researchers applied logistic regression analyses to examine the association between early menopause and selected lifestyle factors. The study showed an association between current smoking and early menopause. The data also suggested that the earlier a woman gives up smoking, the further she is from early menopause .
A recent study investigating the relationship between smoking and menopause followed a large population of Swedish women over 16 years; the authors investigated the difference in median age at death between women with menopause at 40 years and women with menopause at 60 years. The results showed that the difference was 1.3 years. In the same study, the researchers stated that, compared with current smokers, former smokers and never smokers had an older median age at death of 2.5 years .
Hee and colleagues in 2015 performed a study using data from the Korea National Health and Nutrition Examination Survey from 2007 to 2012. They analyzed the menopausal age in relation to smoking as a Kaplan-Meier survival curve for 11,510 women whose age was between 30 and 65 years. They found that the menopausal age among smokers was significantly lower than that among non-smokers .
The above-mentioned data and the results obtained from researches support the messages of the health educators and physicians: smoking is associated with early menopause; it can be prevented by quitting smoking; results for former smokers are similar to those who have never smoked.
A very interesting fact is that cigarette smoking, which decreases the age at menopause, has been identified as the only lifestyle factor modifying this association. This fact is really promising for those who want to prevent the health problems related with early menopause.
Assistant Professor, Basic Medical Sciences, University of Sharjah
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