Association between grandparent coresidence and weight change among first-grade Japanese children

The prevalence of grandparent coresidence is increasing. However, the impact of grandparent coresidence on weight change among school-age children remains unclear.

The objective of the study is to examine the association between grandparent coresidence and obesity-related behaviours and change in body mass index (BMI) z scores among school-age children.

In total, 3422 caregivers of first-grade children in Adachi City, Tokyo, participated in surveys and health checkups in 2016 and 2017 with no change in their grandparent coresidence status (response rate: 80.1% and 81.4%, respectively). Association between grandparent coresidence and obesogenic dietary, physical activity, and screen-based sedentary behaviours was measured using Poisson regression with robust error variance analysis, while change in BMI z scores was determined by linear regression and adjusting for potential covariates.

Grandparent coresidence was associated with increased prevalence rate (PR) of irregular snack foods intake (PR: 1.38, 95% confidential interval (CI): 1.19, 1.61); however, children who live with grandparents showed a lower BMI z scores in the second grade (coefficient: -0.048, 95% CI: -0.094 to -0.0013) after adjustment for BMI z scores in the first grade, family sociodemographics, and obesogenic behaviours.

Grandparent coresidence is associated with lower BMI z scores among early primary school-age Japanese children living in urban areas.