Sleep disturbances and delayed sleep timing precede neurological disease

Sleep disturbances have been linked to an increased risk of neurological disease, but it remains unclear whether they represent modifiable risk factors or early signs of disease. We investigated how multiple dimensions of sleep relate to the onset of neurological disease, and whether sleep patterns change before and after diagnosis. We used longitudinal data from 24,033 participants in the Swedish Longitudinal Occupational Survey of Health, followed biennially from 2010 to 2018. Incident neurological disease was identified via national registers. Associations were analyzed using Cox proportional hazards models and longitudinal trajectories of sleep variables were examined using linear mixed-effects models on a backward timescale. During a median follow-up of 4 years, 1382 participants developed a neurological disease. Several sleep-related symptoms were associated with increased risk, including persistent fatigue (HR 1.58, 95% CI 1.38-1.80), non-refreshing sleep (HR 1.40, 95% CI 1.22-1.62), and sleep-disordered breathing (HR 2.27, 95% CI 1.75-2.93). Insomnia alone was not associated with increased risk (HR 1.06, 95% CI 0.84-1.33), unless accompanied by daytime symptoms (HR 1.51, 95% CI 1.28-1.78). Longitudinal analyses showed that individuals who developed neurological disease experienced a gradual shift toward later bed- and wake-up times, along with increasing insomnia symptoms, fatigue, and sleep-disordered breathing in the years preceding diagnosis. Sleep symptoms and changes in sleep-wake timing precede the diagnosis of neurological disease by several years. These patterns may reflect early prodromal alterations in brain function and support the potential of sleep-related complaints as early indicators in neurological health surveillance.