Some adult neurological complications of obesity may have early-life origins. Here, we examine associations of childhood hearing impairment with childhood and adult obesity, among 3288 male and 3527 female members of a longitudinal cohort born in Great Britain in 1970. Height and weight were measured at age 10 years and self-reported at 34 years. Audiometry was conducted at age 10 years. The dependent variable in logistic regression was minor bilateral hearing impairment as a marker of systemic effects, while BMI at age 10 or 34 years were modelled as independent variables with adjustment for potential confounding factors including social class, maternal education and pubertal development at age 10 years. Among females, the adjusted odds ratios (and 95% confidence intervals) for hearing impairment at age 10 years were 2.33 (1.36-3.98) for overweight/obesity; and at age 34 years they were 1.71 (1.00-2.92) for overweight and 2.73 (1.58-4.71) for obesity and the associations were not explained by Childhood BMI at age 10 years. There were no consistent associations among males and interaction testing revealed statistically significant effect modification by sex. The dose-dependent associations among females are consistent with childhood origins for some obesity-associated impaired neurological function and the possible existence of a 'pre-obese syndrome'. The accumulation of risks for poorer health among those who become obese in later life begins in childhood. Childhood exposures associated with bilateral hearing impairment are risks for obesity in later life among females.