Psychosocial Risk Factors and Alzheimer's Disease: Depression and Sleep Disturbance

Background: Alzheimer’s disease dementia (AD) is a neurodegenerative condition, which causes clinically observable impairments in cognition and memory. Within the United States, AD is the most common form of dementia in the elderly, affecting 1 in 9 people over the age of 65, and 32% of those age 85 and over. Sleep disturbance has been called a ‘public health epidemic’ and, like depression, is a prodromal symptom of AD but may also contribute to the risk of developing AD. The authors hypothesized that sleep disturbance, depression symptoms in the last two years and lifetime depression, independently, and in combination, increase the hazard of AD.

Methods: Data from the National Alzheimer’s Coordinating Center Uniform Data Set was utilized to analyze evaluations of 11,453 participants, deemed to be asymptomatic at visit one. Assessments from 2005 to September 2014 were included. Survival analysis was used to explore the relationships between depression symptoms and sleep disturbance as predictors of AD. Cox proportional hazard models were utilized to explore main effects and synergistic interactions among the predictor variables.

 Results: Those experiencing both recent depression symptoms and sleep disturbance were twice as likely to receive the AD diagnosis (HR=4.89 [95% CI 3.46-6.92]) than those who were not depressed but experienced sleep disturbance (HR=2.61 [1.85-3.70]) and those who reported depression symptoms but did not experience sleep disturbance (HR=2.31 [1.75-3.05]). The effect of lifetime depression and sleep disturbance in relation to AD indicated a strong positive relationship (HR=3.19 [2.14-4.77] p < 0.001). Clinician-verified depression and sleep disturbance was also strongly correlated (p < 0.001) with eventual AD diagnosis; yielding a hazard three times greater (HR=3.95 [2.53-6.17]) than those without such symptoms.

 Conclusion: Findings suggest that sleep disturbance, as well as recent and historical depression symptoms are associated with AD among initially cognitively asymptomatic participants. This study contributes to the literature exploring an increased hazard of AD due to potentially modifiable psychosocial factors. Modifiable psychosocial and behavioral factors are prime intervention sites for social workers and other human service professionals. Currently, AD has no cure and few effective treatments. If the aforementioned symptoms are independent risk indicators as opposed to prodromal neurodegeneration symptoms, decreasing their hazard may be one avenue for possibly delaying onset of Alzheimer’s disease dementia.