<p>We previously found that seasonal changes in sleep duration were affected by sex, residential area, and age in Japanese community residents. This study aimed to determine whether these factors also affect the seasonality of insomnia-related symptoms (IRS) and clarify specific seasonal differences in the frequency of IRS in the Japanese population adjusting for these factors. A detailed re-analysis of the data of Japanese community residents used in our previous study was performed. Longitudinal data of 1568 individuals aged 15–89&#xa0;years, with each participant providing responses at four time points (spring, summer, fall, and winter) were analyzed. The participants answered a questionnaire including items on IRS (difficulty initiating sleep [DIS], difficulty maintaining sleep [DMS]/early morning awakening [EMA], and excessive daytime sleepiness [EDS]). A mixed-effects ordinal logistic model was used to assess the effects of sex, region of residence, and age on seasonal variations in IRS and specific seasonal differences in the frequency of IRS adjusting for these demographic factors. All IRS were more frequent in spring and summer than in fall and winter. Age affected the seasonality of DMS/EMA. The young and middle-aged groups showed seasonal variation in DMS/EMA frequency, whereas the elderly group showed no seasonal variation. Sex and residential area showed no significant effect on the seasonality of any IRS. The seasonality of IRS seems to be unaffected by demographic factors as much as the seasonality of sleep duration, with only DMS/EMA being affected by age. The specific interseasonal differences in IRS frequency in the Japanese population were revealed.</p>