Sleep-disordered breathing (SDB) is a very common but treatable condition in older adults. There has been growing interest in the relationship between SDB and adverse health consequences, including hypertension, diabetes, and cardiovascular diseases.^1-4 While the association between SDB and health outcomes remains controversial, especially in older populations,^5-8 recent evidence has suggested a link between SDB and cognitive decline in elderly persons.^9-11 Notably, most early studies have examined the association between SDB and cognition in clinical populations, eg, among patients at sleep clinics.^12-14 These studies usually consist of individuals with relatively severe SDB and were limited by small sample sizes and failure to account for confounding factors.

Parkinson disease (PD) represents one of the fastest-increasing number of cases among neurological disorders, characterized by early death of dopaminergic neurons in the substantia nigra.¹ Importantly, PD pathology involves much more extensive brainstem neurotransmitter systems far outside the basal ganglia and occurs years or decades before dopaminergic neuronal death.² The multiple neuronal groups and areas affected by PD pathology, such as cholinergic, serotoninergic, and noradrenergic neurons in the brainstem and orexinergic neurons in the posterolateral hypothalamus,^3-6 play a key role in the development of sleep-wake disturbances, which is the most common nonmotor symptom in patients with PD.⁷

Objective To test the hypothesis that veterans with traumatic brain injury (TBI) have an increased subsequent risk of sleep disorders, we studied the longitudinal association between TBI and incident sleep disorders in nearly 200,000 veterans. Methods We performed a cohort study of all patients diagnosed with a TBI in the Veterans Health Administration system from October 1, 2001, to September 30, 2015, who were age-matched 1:1 to veterans without TBI. Veterans with prevalent sleep disorders at baseline were excluded. Development of sleep disorders was defined as any inpatient or outpatient diagnosis of sleep apnea, hypersomnia, insomnia, or sleep-related movement disorders based on ICD-9 codes after the first TBI diagnosis or the random selection date for those without TBI. We restricted the analysis to those with at least 1 year of follow-up. We used Cox proportional hazards models to examine the association between TBI and subsequent risk of sleep disorders. Results The study included 98,709 veterans with TBI and 98,709 age-matched veterans without TBI (age 49 ± 20 years). After an average follow-up of 5 (1–14) years, 23,127 (19.6%) veterans developed sleep disorders. After adjustment for demographics, education, income, and medical and psychiatric conditions, those who had TBI compared to those without TBI were 41% more likely to develop any sleep disorders (hazard ratio 1.41 [95% confidence interval 1.37–1.44]), including sleep apnea (1.28 [1.24–1.32]), insomnia (1.50 [1.45–1.55]), hypersomnia (1.50 [1.39–1.61]), and sleep-related movement disorders (1.33 [1.16–1.52]). The association was stronger for mild TBIs, did not differ appreciably by presence of posttraumatic stress disorder, and remained after a 2-year time lag. Conclusion In 197,418 veterans without sleep disorders, those with diagnosed TBI had an increased risk of incident sleep disorders over 14 years. Improved prevention and long-term management strategies for sleep are needed for veterans with TBI.