Background Compared to children and adults, little is known about changes in adolescent health over time. This study profiles the health of preadolescents in two distinct time periods, 1980 and 2012.

Methods Secondary analysis of the British Cohort Study and the Millennium Cohort Study for preadolescents mostly aged between 10 and 11.5 years (range 9.75–13 years). The prevalence/average of, and socioeconomic gradients in, the following were compared between 1980 and 2012; general health problems, anthropometrics, allergic conditions, infectious diseases, health service use, smoking and parental smoking behaviour and maternal adiposity. Socioeconomic status was measured by familial income (3 groups).

Results There were decreases in the proportion of hospital admissions (Δ=−0.10(−0.09:−0.11)) smoking (Δ=−0.12(−0.11:−0.13)), parental smoking (mother: (Δ=−0.19(−0.18:−0.21)) father: (Δ=−0.35(−0.34:−0.37), infectious diseases (measles: (Δ=−0.46(−0.45:−0.47)) whooping cough: (Δ=−0.07(−0.06:−0.07)) and hearing problems (Δ=−0.04(−0.03:−0.05)). There were no changes in limiting long-standing illness (Δ=0.00 (−0.00:0.00)), or the proportion of children having two or more accidents requiring medical attention (Δ=−0.02(−0.00:−0.02)). There were increases in the proportion overweight (Δ=0.18(0.17:0.19)), maternal overweight(Δ=0.22(0.21:0.23)) and obesity(Δ=0.12(0.11:0.13)), height for age(Δ=0.47(0.44:0.49)), weight for age (Δ=0.68(0.65:0.71)), proportion reporting chicken pox (Δ=0.28(0.27:0.29)), allergic conditions (eczema Δ=0.19(0.18:0.20)), asthma Δ=0.12(0.11:0.13), hay fever Δ=0.15(0.14:0.16)) and wearing glasses (Δ=0.08(0.07:0.09)). There were increases in socioeconomic gradients for limiting long-standing illness, smoking, overweight, weight for age, height for age, wearing glasses, asthma and the onset of puberty.

Conclusions There have been reductions in infectious diseases and tobacco exposure among British preadolescents, but overweight and allergic conditions have risen dramatically. Children from deprived families have benefitted least from improvements in health status, and have experienced the largest increases in health risks.