Sibling Resemblance in Physical Activity Levels: The Peruvian Sibling Study on Growth and Health

BACKGROUND

Physical activity (PA) is crucial for health, but global inactivity is high, including in Peru. Sibling resemblance in PA is understudied, especially in diverse environments like Peru's. This study aimed to estimate sibling resemblance in PA and investigate associations with individual characteristics and shared environment. Methods: The study analyzed 247 siblings from 110 families across three Peruvian regions (sea-level, Amazon, high-altitude). PA was objectively measured with pedometers over five days, yielding steps/day and moderate minutes/day. Multilevel models estimated intraclass correlations (ρ) and adjusted for age, BMI, and geographical area. Key Results: Significant sibling resemblance was found for steps/day (ρ=0.44, 95% CI 0.31–0.58) and moderate minutes/day (ρ=0.35, 95% CI 0.22–0.51). No significant differences in ρ were found between sibling types (brother-brother, sister-sister, brother-sister) after adjustments. Sister-sister pairs tended to take fewer steps than brother-brother pairs (β=−2908.75, p<0.05). Older siblings took fewer steps (β=−81.26, p<0.05), while BMI was not significant. Siblings in high-altitude and Amazon regions took more steps than those at sea-level (β=2508.92 and 2213.11, respectively, p<0.05). Limitations: The sample may not be representative of all Peruvian siblings; genetic and environmental influences could not be separated (no twins); socioeconomic status was not adjusted for. Implications: Results suggest genetic factors may primarily drive sibling resemblance in PA, but environmental features (e.g., geographical region) also play a role.