A Study on the effects of seasonal variations in cognitive function on driving behaviour

Background The population in Japan is ageing, and approximately 30% of the elderly are said to have Alzheimer’s disease. On the other hand, however, there are areas with insufficient transport services due to the declining birth rate, and the elderly have to drive cars. In order to reduce accidents caused by drivers with dementia, it is necessary to know the relationship between cognitive function and driving, but cognitive function is said to fluctuate daily. The aim of this study is to obtain knowledge that contributes to the prediction of accidents by observing the seasonal variation in cognitive function and driving using the same subjects. Method A cognitive function test, a driving skill test at a driving school and an observation 1‐month survey of driving behaviour on public open roads were conducted on 40 drivers aged 70 years or older who drive their cars daily. The survey was conducted twice on the same subjects, once between April and June and once between October and December. From the data obtained, seasonal differences were verified. Result It is said that elderly drivers often drive short distances in their neighbourhood, but in reality they also make long trips. Comparing spring/summer and autumn/winter, autumn/winter drivers are more likely to be in a state of cognitive decline and drive more unevenly. Conclusion Cognitive function and driving behaviour of older drivers differ depending on the season. As the passage of time and more short‐term fluctuations may have an impact, it is important to systematise the fluctuating changes in various cycles and link them to safe driving support.