Canadian researchers have found that the cognitive abilities of older adults living with and without dementia shift according to the seasons. The results may have implications for the accuracy of dementia diagnoses and also provide grounds for increased care during periods of seasonal decline.
Researchers found that the participants’ abilities were at their peak in the summer/early autumn and fell into relative decline during the winter/spring period. The average shift in cognitive abilities translated to 4.8 years of age-related decline, and in addition, the chances for meeting the diagnostic criteria for dementia or mild cognitive impairment were higher and lower in the same respective periods.
Even after the team’s data were controlled for factors like sleep, levels of physical activity, and depression, the correlation between season and cognitive function remained strong.
Data on 3,353 people from three cohorts were studied, comprising the US, Canada, and France respectively. Multiple cognitive tests were applied to measure the participants’ abilities, but some were also tested for levels of Alzheimer’s-related proteins and genes in the brain and cerebrospinal fluid that bathes the brain and spinal cord. Similar to the results of the cognitive tests, these levels were found to be elevated in winter months.
The association between seasonal dynamics and brain functions and human behaviour has previously been explored in other areas such as symptom onset in schizophrenia and Seasonal Affective Disorder (SAD).
Potential for a new form of treatment for Alzheimer’s?
The authors acknowledged multiple limitations on the study, such as the fact that all participants were from a temperate northern-hemisphere climate and were only tested once per annual cycle.
This means that in each cohort, there were participants whose data was sourced at various times of year, but when all three cohorts were assessed holistically, those examined during wintertime typically scored worse and vice versa with summertime.
In their concluding remarks, the authors argue there may be value in increasing clinical resources when patients may be enduring peak annual difficulties.
But the most important takeaway is that these results suggest the possibility of a novel treatment for Alzheimer’s disease by figuring out what it is that improves patients conditions in the summertime.
“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,” says co-author Andrew Lim from the University of Toronto.
An exciting discovery, but further research will be needed to solidify the seasonal association and clarify whether or not a new treatment is possible by mastering this mechanism.