Associations of Physical Activity and Lactation Duration With Cardiometabolic Risk Factors: The CARDIA Study

BACKGROUND: Physical activity (PA) and lactation benefit cardiometabolic health. OBJECTIVES: The purpose of this study was to describe the joint associations of PA and lactation with cardiometabolic risk. METHODS: We averaged PA across exams and summed lifetime lactation in Black and White parous women in the Coronary Artery Risk Development in Young Adults Study. Categories were created for PA (−PA: <median; +PA: ≥median) and lactation (−L: <3 months, +L: ≥3 months). Participants were assigned to one of 4 groups: −PA/−L, −PA/+L, +PA/−L, and +PA/+L (most favorable). Cardiometabolic risk factors at the year 30 exam were standardized into a risk score. We evaluated associations of groups with risk factors and risk score using linear regression. Covariates included age, race, study center, parity, education, smoking, medication use, alcohol consumption, and baseline body mass index, and diet quality. RESULTS: The median PA was 256 exercise units and 54% reported lactation duration of ≥3 months. Of 1,068 participants, 303 were in the −PA/−L category, 231 in −PA/+L, 184 in +PA/−L, and 350 in +PA/+L. +PA/+L participants were older, had more years of education, lower body mass index, gained less weight, and less likely to be Black vs −PA/−L participants. Risk scores differed between categories except −PA/+L and +PA/−L (P = 0.08): −PA/−L: 0.23+/−0.04, −PA/+L: 0.08+/−0.04, +PA/−L: −0.02+/−0.05, and +PA/+L: −0.23+/−0.03. After adjustment, +PA/+L was associated with a lower/better risk score (β = −0.15, 95% CI: −0.25 to −0.04). CONCLUSIONS: Above average PA throughout adulthood combined with ≥3 months of lactation was associated with lower risk scores. Participants with either behavior had lower risk vs those with neither behavior. Attaining these levels of behaviors may reduce cardiometabolic risk in parous women.