Objectives: To investigate possible social, lifestyle-related and biological predictors of early menopause in middle-aged women, followed prospectively for 11 years.
Design: A prospective, population-based, cohort follow-up, observational study.
Setting: Glostrup Hospital, Copenhagen, Denmark.
Subjects: A total of 493 female subjects, all aged 40 years at baseline, and divided into three groups according to self-reported menopausal age (40-45, 46-51, 51+ years), after 12 months of amenorrhoea. Women having had medical or surgical interventions to influence menopausal state were excluded.
Main outcome measures: Body mass index, glucose, insulin, lipids, creatinine, uric acid, thyroid-stimulating hormone (TSH), lung function tests (forced VC, FEV1, peak flow), blood pressure; a self-administered questionnaire with questions on psychosocial variables, lifestyle, and self-rated health.
Results: An early menopausal age correlated in an univariate way with impaired lung function, increased smoking habits and low social class (in childhood or present), as well as with a feeling of tiredness, all measured at the baseline investigation. On the contrary, a later menopausal age correlated with higher serum insulin and uric acid levels. In multiple regression analysis, with menopausal age as the dependent variable, it was found that smoking habits (number of years smoking) was inversely (P < 0.001), and insulin as well as uric acid were positively (P < 0.05) correlated with menopausal age.
Conclusions: Females who smoke run an increased risk of early menopause, whereas relative hyperinsulinaemia is independently associated with later menopause. At the age of 40 years, high insulin levels in females might be just a marker for normal female sex hormone physiology, not for insulin resistance, as seen in postmenopausal female subjects. Early menopause might be useful as a potential model of premature ageing.