Insulin Levels Early in Perimenopause Inform Vasomotor Symptom Incidence Across the Menopausal Transition

Metabolic health affects the menopausal transition. Metabolic characteristics like body mass index (BMI) affect vasomotor syndrome incidence, but the role of elevated insulin, an early marker of metabolic dysfunction, remains understudied.

This work aimed to determine whether midlife insulin levels are associated with vasomotor symptom incidence or reproductive hormone trajectories.

Longitudinal analyses of community-based data from the Study of Women's Health Across the Nation (SWAN) were conducted. We analyzed the 704 SWAN participants (of 3302) without oophorectomy or hysterectomy who had metabolic data for age 47 and did not take insulin/medications for hyperglycemia. Mean fasting insulin at age 47 was 10.117 µIU/mL (SD = 6.711), with 27.0 BMI (SD = 6.6); the mean age of the final menstrual period for these participants was 51.0 years (SD = 2.3). Main outcome measures included vasomotor symptom timings and durations, and trajectories of estradiol (E2), follicle-stimulating hormone (FSH), and testosterone (T) across the menopausal transition.

Higher insulin at age 47 predicted younger onsets of hot flashes and night sweats, longer durations of hot flashes and cold sweats, and greater T rise. BMI associations with vasomotor symptoms paralleled those of insulin, but BMI appeared more closely linked to slower E2 decline and blunted FSH rise. In Cox proportional hazards models, elevated age-47 insulin was associated with increased likelihood of hot flashes; this remained statistically significant with BMI and glucose as covariates.

Perimenopausal fasting insulin and BMI show complementary but distinct associations with menopausal changes. Elevated insulin predicts earlier and prolonged vasomotor symptoms, and is associated with higher T.