Alzheimer’s disease symptoms peak in winter and spring

Cognitive skills associated with Alzheimer’s disease in older adults improve during late summer and early fall, while deficits generally occur 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 data of 3,353 participants, all older adults, from three observational community-based cohort studies conducted, in addition to two observational memory-clinic-based cohort studies. These cohort studies were based in the U.S., Canada, and France.

Researchers conducted neuropsychological exams and evaluated levels of genes and proteins particularly associated 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. We examined the association between season and these variables using nested multiple linear and logistic regression models,” the study reads.

Based on the results, researchers determined that cognitive functioning was higher in the summer and fall; winter and spring brought about lower function and increased chances of meeting the diagnostic criteria for mild cognitive impairment. The cognitive effect was similar to 4.8 years difference in age-related decline.

The correlation between seasonality and cognitive function was significant throughout the study. In the findings, researchers also found levels of Alzheimer’s-related proteins and genes in cerebrospinal fluid and the brain that were 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 said.

“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.