Outdoor light at night and neuropsychiatric symptoms in dementia

There is growing interest about the relation between exposure to artificial light at night (LAN) and mental health. This study aims, for the first time, to explore the association between LAN exposure and neuropsychiatric symptoms in individuals with dementia, investigating its role as a potential environmental risk factor. We collected data about 150 patients with dementia in Modena, Italy. We assessed LAN exposure using satellite imagery, while neuropsychiatric symptoms were evaluated through the Neuropsychiatric Inventory (NPI), a caregiver-administered questionnaire measuring the presence and severity of psychiatric symptoms. We used logistic regression models to examine associations between LAN exposure and neuropsychiatric features. Higher LAN exposure was associated with increased risk of psychiatric symptoms, particularly in the domains of psychosis and sleep disturbances. Specifically, individuals exposed to LAN levels above the median (LAN median = 26.32 nW/cm2/sr) demonstrated an elevated risk of delusions, hallucinations, and sleep disturbances (OR = 2.09, 95% CI 0.03–4.25), compared to those in the “below the median” category. Associations with other symptom domains, such as apathy and affective disturbances, showed weaker associations. Our findings indicate that artificial nighttime light exposure may negatively impact the mental well-being of individuals with dementia, potentially exacerbating psychotic symptoms and sleep disturbances. However, caution is warranted when interpreting these results due to the limited sample size and the possibility of unexamined residual confounding.