No seasonality in cognitive performance among adolescents at a subarctic latitude (69°N)

Seasonal changes in daylight are substantial in subarctic areas and are known to affect circadian sleep rhythms. We examined whether seasonality in cognitive performance also exists and to what extent seasonality in sleep moderates this relationship. In the city of Tromsø (Norway) at 69°N, 182 adolescents (36% male; mean age 16.8 years) participated in a prospective study. The cognitive measures included verbal and visual memory, verbal learning, psychomotor speed, and problem solving, whereas sleep and sleep‐related problems were recorded via weekly sleep diaries and questionnaires. The results indicated no effect of season on any of the cognitive tests. Seasonality in sleep timing, insomnia, and fatigue were confirmed; however, these variables did not modify the null correlation between season and cognition. The lack of seasonality in cognition is a positive finding and serves to undermine myths about the burdens of living in subarctic areas with substantial seasonal changes in daylight.