Individual and dual trajectories of insomnia symptoms and body mass index before and after retirement and their associations with changes in subjective cognitive functioning

Background: We examined individual and dual trajectories of insomnia symptoms and body mass index (BMI) before and after retirement, and their associations with changes in subjective cognitive functioning after retirement. Methods: We used the Helsinki Health Study's (n = 2360, 79% women, aged 40-60 at baseline, Finland) repeated surveys to identify the developmental patterns of insomnia symptoms and BMI (2000-2017) and changes in subjective cognitive functioning (2017-2022). We analysed the data using latent group-based dual trajectory modelling and logistic regression analysis. Results: Three latent groups were identified for insomnia symptoms (stable low, decreasing and increasing symptoms) and BMI (stable healthy weight, stable overweight and stable obesity). Insomnia symptoms were associated with declining subjective cognitive functioning and largely explained the effects in the dual models. Conclusion: The association between dual trajectories of insomnia symptoms and BMI with subjective cognitive decline is dominated by insomnia symptoms.