Association of total lifetime breastfeeding duration with midlife handgrip strength: findings from Project Viva

BACKGROUND: Lactation has long term effects on maternal health, but the relationship between lactation and long-term handgrip strength, a marker of musculoskeletal function and healthy aging, has not been explored. OBJECTIVE: Examine the relationship between total lifetime breastfeeding duration (BFD) and midlife handgrip strength. METHODS: We measured handgrip strength as a marker of overall strength among 631 women in the Project Viva cohort. At the same visit, women reported their BFD for each birth, and we derived total lifetime BFD. We used multivariable linear regression models to estimate associations of lifetime BFD in months with midlife handgrip strength in kilograms, adjusted for race/ethnicity, education, marital status, household income, age at first pregnancy and age at handgrip strength assessment. RESULTS: Mean (standard deviation) age was 50.7 (5.1) years, lifetime BFD was 21.6 (19.5) months, and handgrip strength was 28.0 kg (6.0) in the dominant and 26.0 kg (5.6) in the non-dominant hand. In fully adjusted models, each 3-month increment in lifetime BFD was associated with 0.10 kg (95% CI 0.02, 0.18) higher handgrip strength for the dominant hand and 0.10 kg (95% CI 0.03, 0.18) for the nondominant hand. Results were similar in models examining mean BFD per pregnancy rather than total BFD. There was no evidence of effect modification by race/ethnicity. CONCLUSIONS: Our study suggests that there is a small beneficial effect of lifetime BFD on handgrip strength. Future studies can explore mechanisms by which BFD affects body composition and associations with other outcomes related to lean mass such as sarcopenia. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12905-022-01880-1.