Qian, Y.Perret, J.L.Hamilton, G.S.Abramson, M.J.Lodge, C.J.Bui, D.S.Ali, G.B.De Silva, A.P.Adams, R.J.Thompson, B.R.Erbas, B.Walters, E.H.Senaratna, C.V.Dharmage, S.C.2025-06-042025-06-042025Respirology, 2025; 30(5):435-4451323-77991440-1843https://hdl.handle.net/2440/144989Background and Objective While short-term weight changes are known to influence obstructive sleep apnoea (OSA), the impact of body mass index (BMI) changes over the life course has been poorly documented. We examined the association between BMI trajectories from childhood to middle age and adult OSA, 10 years later. Methods Five BMI trajectories were previously identified in the population-based cohort Tasmanian Longitudinal Health Study (TAHS), using eight time-point BMI from age 5 to 43 years. The primary outcome was probable OSA at 53 years, defined using STOP-Bang questionnaire, with Berlin and OSA-50 questionnaires used to ensure consistency of findings. Clinically significant diagnosed OSA was defined as self-reported medical diagnosis or mild OSA with symptoms or moderate-to-severe OSA, using type-4 sleep studies. Associations were examined using multivariable logistic regression. Results Compared with the average BMI trajectory, the child average-increasing (aOR = 5.28, 95% CI 3.38–8.27) and persistently high trajectories (aOR = 3.73, 2.06–6.74) were associated with increased risk of probable OSA. These associations were consistent when using clinically significant diagnosed OSA (child average-increasing trajectory: aOR = 2.95, 1.30–6.72; high trajectory: aOR = 2.23, 0.82–6.09). Individuals belonging to the low trajectory were less likely than the average trajectory to have OSA. Notably, the child high-decreasing trajectory was not associated with OSA. Conclusion Physicians and the public should be aware of the potential risk of OSA in middle-aged adults when BMI is high or continuously increasing from childhood to mid-40s. Obese children who subsequently lose weight were not at higher risk of OSA in middle age—a novel and key finding.en© 2025 The Author(s). Respirology published by John Wiley & Sons Australia, Ltd on behalf of Asian Pacific Society of Respirology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.BMIbody mass index trajectorieshome sleep apnoea testinglongitudinal risk factorsobstructive sleep apnoeascreening questionnairessleep‐disordered breathingSleep Apnea, ObstructiveBody-Weight TrajectoryJournal article10.1111/resp.70002731540Adams, R.J. [0000-0002-7572-0796]