Environmental, Lifestyle, Medical, and Dietary Factors Associated With Hie (Subjective Coldness) Among Japanese Women: A Web-Based Cross-Sectional Survey.

Introduction Hie (subjective coldness or sensitivity to cold) is a common complaint among Japanese women and has been discussed in relation to lower back pain and reduced well-being. Because subjective complaints often do not correspond to measured skin temperatures, environmental, lifestyle, medical, dietary, and psychosocial factors may contribute to the perception of Hie. This exploratory, hypothesis-generating study aimed to identify environmental, lifestyle, medical, and dietary factors associated with Hie status and symptom severity among Japanese women, with a focus on differences between mild (Hie (+)) and severe (Hie (++)) symptoms. Methods We conducted a web-based cross-sectional survey using an online Japanese research panel. Invitations were sent to 5,000 women selected through stratified random sampling by region; 1,000 women completed the survey. For the present analysis, we included only respondents who completed the entire survey and who indicated interest in the topic of Hie in a screening item, yielding a final sample of 341 women. Participants were categorized into three groups: (1) Hie (-): non-Hie group (n=162); (2) Hie (+): mild Hie group (n=114); and (3) Hie (++): severe Hie group (n=65), based on self-reported sensitivity to cold. Group differences were examined using chi-square tests or Fisher's exact tests, as appropriate (two-sided p<0.05). The survey was conducted on January 20, 2022 (midwinter in Japan). Results Compared with the Hie (+) group, the Hie (++) group more often reported a present room temperature of <18°C (p=0.02) and used local/no heating rather than whole-room heating (p<0.01). Ongoing dietary restriction and nocturia ≥two times/night were also more common in the Hie (++) group (p<0.05). In contrast, the Hie (+) participants more commonly reported frequent intake of fish, beans, and fermented foods (p<0.05). Among analgesic users, the Hie (+) group more commonly obtained analgesics from drug stores/the Internet and used them mainly to manage menstruation symptoms, whereas the Hie (++) group more often obtained them from friends/family and used them for other pain/fever (Fisher's exact tests, p<0.05). Conclusion Mild and severe Hie showed distinct association patterns. Severe Hie was associated with a present room temperature of <18°C, less whole-room heating, ongoing dietary restriction, and more frequent nocturia, whereas mild Hie was associated with higher intake of fish/beans/fermented foods and different self-medication patterns among analgesic users. Because this was a cross-sectional survey, causality cannot be inferred; prospective studies with objective measures and broader covariate assessment are warranted.