The effect of light exposure on cognitive outcomes at long term follow up in an at‐risk dementia population

Abstract

AbstractBackgroundCircadian disturbances are a common occurrence in older adult population but are more prevalent in people with dementia. For some individuals, these occurrences begin many years prior to the onset of clinical symptoms and have been suggested as a potential risk factor. As light is the primary synchroniser of the circadian system, the current study aimed to examine if 14‐day light exposure could predict cognitive outcomes of older adults with varying risks of dementia at 2‐year follow‐up.MethodThe study was a retrospective analysis of 195 participants (age = 67, 60.7% female) who attended the Healthy Brain Ageing Clinic in Sydney. At baseline, participants were neurocognitively assessed and wore an actigraph for 14 days and then completed another neurocognitive test battery at their follow‐up. Binary logistic regression was used to determine if participants converted to either Mild Cognitive Impairment (MCI) or dementia was predicted from light exposure (average and maximum) and average time spent in >1000 lux (OR = 1.00), adjusting for age, sex and years of education. Linear regression was used to investigate the relationship between light variables and differences in verbal memory, processing speed and executive function composite scores from baseline to 2 years.ResultLight exposure at 2 years prior did not appear to predict cognitive performance. There was a trend towards moderate to bright light increasing risk of cognitive decline.ConclusionFurther research is needed to understand light exposure and the relationship to circadian rhythms and cognition. As previous light therapy research has been inconclusive, future research will inform treatment approaches.