Chapter 31: Menopause and Perimenopausal Issues

SCOPE OF THE ISSUE OF OBESITY IN THE MENOPAUSAL TRANSITION

Menopause is defined as the natural end to a woman’s menstrual cycle at the average age of 51 years and ranging between 45 and 55 years.¹ This period of time may also be associated with physiologic symptoms, such as vasomotor symptoms or “hot flashes,” mood lability, anxiety, depression, weight gain, insomnia, and fatigue. Many of these symptoms have been attributed to the menopausal transition secondary to a decline in ovarian function.¹ The percentage of obese individuals in our population can be assessed through the National Health and Nutrition Examination Survey (NHANES). The 2011–2012 survey data were assessed for body mass index (BMI) stratification²; they revealed that 33.9% of US adults aged 20 years and older were overweight, 35.1% were obese, and 6.4% were extremely obese, with a BMI greater than or equal to 40. These numbers jump significantly in the perimenopausal period. When assessed in the NHANES data set last so stratified in 2007 (showing no change in trends since 2003–2004), 41.1% of women aged 40–59 were obese compared to 30.5% aged 20–39 years. When evaluated by ethnicity, 53% of non-Hispanic black women, 51% of Mexican women, and 39% of non-Hispanic white women aged 40–59 were obese. Over age 60, these numbers increased to 61% for non-Hispanic black women but decreased to 37% for both non-Hispanic white and Mexican women.³ Baseline obesity can affect many of the symptoms described as well as potentially affect the perimenopausal-to-menopausal transition.¹

TIMING OF ONSET OF OBESITY

The physiology of menopause in all women surrounds the cessation of ovulation due to a loss of ovarian follicles, which in turn reduces ovarian production of estradiol, the most biologically active form of estrogen. This process then will cause an increase in circulating follicle-stimulating hormone (FSH) and a decrease in inhibin, which inhibits the release of FSH. The elevated FSH also increases the rate of follicular loss.⁴ Menopause is reached when the follicular number reaches approximately 1000.⁵

There has been some debate regarding the impact of obesity on the timing of menopause. There are studies that discussed an increase in BMI as positively associated with a later onset of menopause, using elevation of hormonal levels as a marker for timing.^6,7 There are also as many studies that showed no association between BMI and age of menopause onset. One study showed a modest prolongation of the age of menopause from 50.1 years to 50.4 years but using a BMI of 21.9 and 26.2, respectively.⁸ It is clear in these studies that current smoking was associated with an earlier age of menopause, and increasing parity delayed onset of menopause, but these are additional confounding factors in many of the studies in assessing obesity.^9,10 As the current existing data stand, obesity independent of smoking, parity, and exercise ...