Cognitive ability in people over 70 is much sharper in summer and autumn than in the winter months, according to a new study. Researchers from the University of Toronto have suggested that screening patients for dementia in the winter and spring can be more effective due to seasonal flare ups in the tell-tale proteins.
The large-scale study took into account information from patients living in Canada, the US and France. It found that the brains of healthy elderly people who took part seemed 4.8 years younger in the summer and autumn than they did between the months of November and May.
As for those with Alzheimer’s, they also experienced dips in winter, when seasonal rhythms caused certain proteins to express dementia-related genes more prominently in the brain. While there is still no definitive test for neurodegenerative diseases, assessing them during these months could lead to more accurate diagnoses.
Dr Andrew Lim, assistant professor of neurology at the University of Toronto and lead author of the study, said: “This association was independent of mood, sleep, physical activity, and thyroid status.
“It was clinically significant, as reflected in a nearly 30 per cent higher odds of meeting criteria for mild cognitive impairment or dementia in winter and spring compared to summer and fall, and it persisted in cases with pathologically confirmed Alzheimer's disease.”
He added that it might be worth adding clinical resources to the area of neurological disease during the winter and early spring. When symptoms are more pronounced and demand is therefore likely to be higher, medical facilities could be better prepared, due to these findings.
There are a number of theories as to why the brain could be affected so much by the seasons. The first, outlined by Dr Lim, is to do with environmental factors and includes accessibility of light and warmer temperatures, which could work to boost cognition in the summer and autumn.
If it can be proved that this is the case, then phototherapy and manipulating temperatures for the elderly could be effective treatments. Sustaining the peak experienced in summer could lead to a better quality of life throughout the whole year.
Secondly, during the summer months people tend to be more active, eat a healthier diet and sleep better. All of these areas can have an impact on cognition, but were not measured in this particular study. Further research could ask participants to report on these aspects of their life to ascertain greater insight.
Thirdly, seasonal depressive disorder affects a lot of people in the winter and such a psychological state could be a contributing factor. Again, this was not assessed in the Toronto University research, but could be worth investigating in future.
The last theory takes all of these factors into account – environmental, lifestyle and psychological – and suggests they have an effect on hormone and vitamin levels. Among those with levels that can change with the seasons and have an impact on cognition are vitamin D, melatonin, testosterone and other sex hormones.