ObjectiveTo describe the prevalence of multimorbidity among individuals with premature ovarian insufficiency (POI) and early menopause, in comparison to average age of menopause. DesignProspective cohort SubjectsThis prospective cohort encompassed female postmenopausal individuals from the Canadian Longitudinal Study on Aging (CLSA). The CLSA collected cross-sectional data from 50,000 community-dwelling Canadians aged 45 to 85 between 2010 and 2015. ExposureThe primary exposure was primary ovarian insufficiency (defined by onset of menopause younger than 40 years). Comparators included average age of menopause (age 46 to 55 years), early menopause (40-45 years), late onset menopause (56-65 years), and those who underwent a hysterectomy. Main outcome measuresThe primary outcome was multimorbidity, which was defined as two or more chronic conditions. The secondary outcome was severe multimorbidity (defined as three or more chronic conditions) as well as frequencies of specific chronic conditions among a comprehensive list of 15 individual conditions. We assessed the association between multimorbidity and age at menopause using logistic regression and odds ratios, with confidence intervals set at 95%. Odds ratios were adjusted for known predictors of multimorbidity, including age, menopause hormone therapy (MHT), education, ethnicity, self-reported loneliness, living alone, BMI, smoking habits, nutritional risk, social participation, and physical activity. ResultsA total of 12,339 postmenopausal participants were included, of which 374 (3.0%) experienced POI and 1396 (11.3%) experienced early menopause. The prevalence of multimorbidity was 64.8% and 51.1% among those with POI and early menopause respectively. In contrast, only 43.9% of individuals with average age of menopause (age 46 to 55 years) had multimorbidity. The OR for multimorbidity in the POI population was 2.5 (95% CI 2.0-3.1) in comparison to those who underwent the average age of menopause. This relationship was maintained after adjustment for confounders (aOR 2.0, 95% CI: 1.5-2.5). The prevalence of severe multimorbidity was also double in the POI group in comparison in the average age group (39.2% versus 21.1%). There was significantly increased risk of ischemic heart disease (aOR 2.8, 95% CI: 1.7-4.7), gastric ulcers (aOR 1.6, 95% CI: 1.1-2.3) and osteoporosis (aOR 1.6, 95% CI: 1.2-2.1) in the POI group. ConclusionsIndividuals with POI and early menopause experience increased multimorbidity in comparison to those undergoing menopause at an average age. This trend persists even after adjusting for significant multimorbidity risk factors.