Abstract
Insomnia is a significant public health problem; however, no research has conducted a spatial analysis on insomnia in Japan. Therefore, this study aimed to identify potential spatial clusters of insomnia and its related factors among prefectures and to explore the factors associated with insomnia at the prefecture level in Japan. Data from the Japan COVID-19 and Society Internet Survey (JACSIS 2023) was used to estimate the percentages of smokers, alcohol drinkers, and insomniacs for each prefecture using Bayesian statistics. Getis-Ord Gi* spatial statistics was applied to identify potential clusters for all factors. Additionally, Global Ordinary Least Squares (OLS) regression was conducted to examine factors associated with insomnia at the prefecture level in Japan. The percentage of smokers, alcohol drinkers, and individuals with insomnia in the overall population ranged from 19.2 to 23.4%, 44.6-55.7%, and 8.7-15.8%, respectively. The percentages of smokers and alcohol drinkers were higher among males than females, whereas the percentage of insomnia was greater among females. The hot spots for social welfare expenditure are notably concentrated in the western regions, while the cold spots are concentrated in the central areas of Japan. A similar pattern was observed among the male population for the percentages of smokers, alcohol drinkers, and insomniacs. The factors associated with insomnia differed between males and females. In the male model, percentage of smokers was positively associated with percentage of insomniacs (b = 0.875, p-value < 0.001), whereas in the female model, social welfare expenditure of each prefecture had a significant positive effect on percentage of insomniacs (b = 0.091, p-value = 0.003). In conclusion, smokers, alcohol drinkers, social welfare expenditure and individuals with insomnia exhibit spatial variations and clustering across Japan's prefectures. Percentage of smokers has a significant positive association with percentage of insomniacs among males, while social welfare expenditure has a positive association with percentage of insomniacs among females.