Association between Volunteer Activity Participation and Daily Sedentary Time among Adults in Japan: A Cross-sectional Study

Introduction Sedentary behavior, involving low energy expenditure while sitting or reclining, is linked to health risks. Volunteering may help reduce sedentary time through social interaction and physical activity, but this relationship is understudied in non-Western contexts. This study investigated the association between volunteer activity frequency and daily sitting time among adults in Aichi and Kanagawa Prefectures, Japan, regions with higher aging. Methods A cross-sectional study was conducted in two regions of Japan, with a sample of 1,224 adults (585 men and 639 women) from these regions. Data on volunteer activity frequency and daily sitting time were collected using questionnaires. Multiple regression models explored the relationship between volunteer frequency and sitting time, adjusting for confounders. Results The mean daily sitting time was 357.66 ± 240.40 minutes. Participants volunteering four or more times weekly reported significantly shorter sitting times compared to non-participants, with an average difference of 131.96 minutes (95% CI: -253.83 to -10.08) in the multivariable-adjusted model. This association was stronger among males (difference: 180.51 minutes; 95% CI: -353.84 to -7.28) and older adults aged ≥65 years (difference of 142.48 minutes; 95% CI: -272.58 to -12.38). Conclusion Frequent volunteering is associated with shorter sitting times, particularly among males and older adults. However, due to the cross-sectional design, causal inferences cannot be made, and the associations should be interpreted with caution. Compared to Western populations, sitting time was lower, but it still exceeded public health recommendations. Future research should explore the longitudinal effects and identify specific volunteer activities that promote active lifestyles.