A within-subject examination of grandparents' physical activity and sedentary behavior levels in the presence or absence of grandchild care provision.

Background: This study aimed to examine within-subject differences in levels of physical activity (PA) and sedentary behavior (SB) among Flemish grandparents aged 50 years and older during a day of providing versus not providing grandchild care. Additionally, grandparents' PA and SB levels of the specific caregiving moment within the included care day were also compared with those of the corresponding specific time frame on the matching non-care day.

Methods: Data were obtained and pooled from three assessment time points of the Healthy Grandparenting Project. Objectively measured PA and SB levels were assessed through ActiGraphs wGT3x(+) worn during waking hours for seven consecutive days and expressed relative to the total wear time of the selected days or moments (i.e., percentage of time per day or per moment). Generalized linear mixed models were used to evaluate the within-subject differences in grandparents' light intensity PA (LIPA), moderate-to-vigorous intensity PA (MVPA) and SB levels between a care and non-care day as well as between the care and non-care moment of those respective days.

Results: A total of 92 grandparents (64.6 ± 4.8 years, 67.4% women) were included in the analyses. During the care day and care moment, grandparents showed higher relative levels of LIPA (∆=4.0% and ∆=7.9%, respectively) and lower relative levels of SB (∆=3.7% and ∆=6.7%, respectively) as compared to their respective non-care day and non-care moment (all p < 0.001). While there was no significant difference in relative MVPA levels between a day of providing versus not providing grandchild care (∆=0.3%, p = 0.500), the grandparents showed significantly lower relative levels of MVPA during the specific care moment against the non-care moment (∆=1.3%, p = 0.029).

Conclusions: The higher percentage of time of LIPA and lower percentage of time spent on SB during a care day and care moment compared to a non-care day and non-care moment, highlight the positive impact of grandchild care provision on grandparents' activity levels, potentially improving other health-related outcomes. Furthermore, grandparents seem to compensate for their lower MVPA levels during the actual care moment since no differences in MVPA levels were found at day level when compared to a day without grandchild care.

Trial registration: clinicaltrials.gov, Identifier: NTC04307589. Registered March 2020.