Abstract Body (Do not enter title and authors here): Introduction
Changes in body composition throughout the reproductive cycle accelerate during the 2 years following the final menstrual period (FMP), known as the menopausal transition (MT). During MT, an increase in fat mass (FM) and a decrease in fat free mass (FFM) are usually seen, but the relationship between these changes and cardiovascular events is not well understood. We aim to explore how FM and FFM are associated with cardiovascular events and total mortality across the reproductive cycle in participants of the Multi-Ethnic Study of Atherosclerosis (MESA).

Methods
This study included 3439 women from exam 1 of MESA. Outcomes of interest were either MACE (heart failure, myocardial infarction, coronary revascularization, cardiac arrest, or stroke) or all-cause mortality. Equations to determine FM and FFM at exam 1 were validated with the NHANES 2003 population and derived from regression models based on bioelectrical impedance analysis results at exam 5 and anthropometric and demographic measures. Women were divided into 3 groups based on time since FMP: reproductive phase (before FMP), MT phase (<2 years after FMP), and late menopause phase (>2 years after FMP). Adjusted Cox multivariate models assessed the association between FM, FFM and MACE or all-cause mortality.

Results
Median follow-up time was 14.1 years. FM was associated with MACE in the late menopause group, whereas FFM was not associated with MACE (Table). With respect to all-cause mortality, FM had a positive association (HR=1.19, P=0.03) while FFM had a negative association (HR=0.68, P=0.04) in the MT phase. The late menopause group showed similar relationships between FM, FFM, and all-cause mortality. The reproductive group showed no significant associations (Table).

Conclusion
In this cohort, FM is associated with a higher risk of mortality whereas FFM is associated with a lower risk. We observed these associations to be more pronounced during the MT, a time of accelerated body composition change. Our results suggest and will need further investigation to confirm that the MT may be a critical time in the female lifespan to initiate interventions which positively impact muscle mass with a view to improving survival.