Alzheimer’s disease symptoms peak in winter and spring

Cognitive deficits in older patients with Alzheimer’s disease improve during late summer and early fall, but generally worsen in the winter and spring, a new study suggests.

The study, led by researchers at Sunnybrook Health Sciences Centre and the University of Toronto, analyzed the data of 3,353 participants from three observational community-based cohort studies and two additional observational memory-clinic-based cohort studies, based in the U.S., Canada, and France.

Researchers conducted neuropsychological exams and evaluated the levels of genes and proteins correlated with Alzheimer’s disease.

“We performed neuropsychological testing and, in subsets of participants, evaluated cerebrospinal fluid AD biomarkers, standardized structured autopsy measures, and/or prefrontal cortex gene expression by RNA sequencing,” according to the findings. “We examined the association between season and these variables using nested multiple linear and logistic regression models.”

Based on the results, researchers determined that cognitive functioning was higher in the summer and fall. Winter and spring, however, brought forth lower function and increased chances of diagnosis for mild cognitive impairment. The cognitive effect was similar to a 4.8 years difference in age-related decline.

The link between seasonality and cognitive function was significant throughout the study, researchers say. In the findings, they also discovered levels of Alzheimer’s-related proteins and genes in cerebrospinal fluid directly linked to seasonality.

“There may be value in increasing dementia-related clinical resources in the winter and early spring when symptoms are likely to be most pronounced,” researchers suggest.

“By shedding light on the mechanisms underlying the seasonal improvement in cognition in the summer and early fall, these findings also open the door to new avenues of treatment for Alzheimer’s disease.”

The findings were published in the journal PLOS Medicine.