Alzheimer’s disease is the most common form of dementia, affecting nearly 70 per cent of people with dementia. The damaging outcomes of Alzheimer’s include impaired memory, thinking and cognitive function. Many studies have been conducted to understand this condition and research has found an association between the seasons and cognition skills in older adults. To understand this link better, researchers from the Sunnybrook Health Sciences Centre and the University of Toronto in Canada conducted a study that could have important therapeutic implications for the diagnosis and treatment of Alzheimer’s disease.
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Researchers analysed data from 3353 participants from three observational community-based cohort studies of older people with and without Alzheimer’s disease, as well as two observational memory-clinic-based cohort studies. The researchers performed neuropsychological testing and in some participants they also evaluated the levels of proteins and genes associated with Alzheimer’s disease.
The researchers found a robust association between seasons and cognition which was replicated in multiple cohorts. They found that the average global cognitive function in older adults was higher in summer and autumn, compared to winter and spring, with the difference equivalent to 4.8 years of difference in age-related decline. Additionally, the odds of meeting the diagnostic criteria for mild cognitive impairments or dementia were higher in winter and spring than in summer or autumn. These results were robust and the association between seasons and cognition skills function remained significant even after accounting for potential confounders such as depression, sleep, physical activity and thyroid status. The researchers also found an association between seasons and the level of Alzheimer’s-related proteins and genes in the cerebrospinal fluid and the brain. This study reveals that cognition skills in older adults with or without Alzheimer’s disease decline in winter and spring, but are better in summer and autumn.
The study has limitations as the participants were only assessed once per annual cycle and the study only included data on people from the temperate northern hemisphere. However, a significant association was found between seasonal changes and cognitive functioning in older adults with Alzheimer’s disease, which can open avenues for increasing dementia-related resources when the symptoms of Alzheimer’s are more pronounced.
Source: PLOS Medicine
