Actigraphy-measured sleep and growth trajectories during the first two years of life: longitudinal evidence from a birth cohort.

This study aims to examine associations between changes in objectively measured sleep characteristics and growth trajectories, as well as risk of rapid weight gain (RWG) and overweight in infants. The study analyzed data from 298 healthy term infants (48.7% boys) in the Sleep Health in Infancy & Early Childhood (Rise & SHINE) birth cohort, with sleep measured by actigraphy at 1 and 6 months. Changes in nighttime sleep duration, fragmentation (wake after sleep onset [WASO], waking bouts, sleep efficiency), and regularity (sleep regularity index [SRI]) were examined as exposures. Growth trajectory parameters-size, tempo, and velocity-were modeled from repeated anthropometric measurements using SuperImposition by Translation and Rotation (SITAR), and weight outcomes at 24 months included RWG and overweight. Associations between sleep changes and growth outcomes were examined using linear and logistic regression models. In adjusted models, a 1-hour increase in WASO between 1 and 6 months was associated with greater weight size (β = 0.093; 95% CI, 0.019 to 0.166), as well as higher odds of RWG (OR, 2.39; 95% CI, 1.02 to 6.07) and overweight (OR, 2.66; 95% CI, 1.16 to 6.16). A 5% decrease in sleep efficiency was associated with greater weight size (β = 0.059; 95% CI, 0.020 to 0.099) and slower weight velocity(β = -10.013; 95% CI, -18.693 to -1.332). A 5% decrease in the SRI was associated with later length tempo (β = 0.004; 95% CI, 0.001 to 0.007). No associations were observed for sleep changes with weight-for-length trajectories. Early sleep patterns may serve as a modifiable factor in preventing future obesity. Statement of Significance Infant sleep changes rapidly in the first two years, and early disturbances have been linked to outcomes such as obesity. Yet few studies have examined how objectively measured multidimensional sleep changes shape growth trajectories. Using actigraphy data from 1 to 6 months, this study found that greater sleep fragmentation (measured by WASO and sleep efficiency) was associated with larger weight size and higher odds of RWG and overweight at age 2. Decreases in sleep efficiency were also linked to slower weight velocity, while decreases in sleep regularity were associated with later length tempo. These findings suggest that improving infant sleep may help normalize growth and reduce later obesity risk. Future research should explore modifiable factors and guide early strategies to support healthy sleep and growth.