Association between insufficient sleep and mental health in preschoolers: effect modification by low household income.

BACKGROUND: Early childhood mental health problems are prevalent worldwide and can have long-term adverse outcomes. Insufficient sleep has been linked to poorer mental health, but evidence from disadvantaged populations remains limited. We examined this association between insufficient sleep and mental health outcomes in western Chinese preschoolers and whether it varies by demographic and socioeconomic factors. METHODS: 21,366 children aged 3-6 were recruited using stratified cluster sampling from 189 public kindergartens in a non-capital city of western China. Parent-reported daily sleep duration was categorized as <8, 8-<10, and 10-13 hours per day (reference). Mental health was assessed using the Strengths and Difficulties Questionnaire (SDQ), with outcomes as total difficulties (TDS >14) and prosocial behavior (PB <6). Multivariable regression models were used to estimate odds ratios (ORs) and coefficients (β), adjusting for demographic and socioeconomic covariates. Subgroup and interaction analyses were performed to identify effect modification. RESULTS: Among 21,366 children, 18.6% had elevated total difficulties (TDS >14). Compared with children sleeping 10-13 h/d, those sleeping 8-<10 h/d had 45% higher odds of TDS >14 (OR = 1.45), and those sleeping <8 h/d had three-fold higher odds (OR = 3.07). Similar patterns were observed for continuous SDQ scores and prosocial behavior. The association of insufficient sleep with total difficulties decreased gradually across low-income (OR = 1.64), middle-income (60,000-99,999 CNY, OR = 1.34) and high-income households (OR = 1.22; P for interaction = 0.0137), and the association with low prosocial behavior strengthened with age (OR = 1.16 at <4 years; 1.29 at age 4; 1.45 at ≥5 years; P for interaction = 0.0186). CONCLUSION: Insufficient sleep is associated with poorer mental health in preschoolers, with stronger association among children from low-income families. Promoting adequate sleep, particularly in disadvantaged households, could be an effective strategy to improve mental health equity in early childhood.