4.1. Main Analysis
MetS
HOLIDAYS
The present study aimed to examine the association between MetS status and PA level, as represented by step count and active minutes, using Japanese PA reference values recommended by EPAR. The main analysis indicated that the pre-MetS and MetS groups showed comparable associations with both step count and active minutes, respectively, when compared to the no-MetS group. Participants with MetS showed an inverse, albeit non-significant, association with both step count and active minutes compared to those with no MetS. Meanwhile, individuals with pre-MetS showed significant inverse associations with both step count and active minutes. In fact, compared to individuals without MetS, those with pre-MetS had approximately 40% lower odds of reaching their daily recommended step count and active minutes.Our finding that MetS did not show a significant inverse association with PA deviates from the primary hypothesis. The following may explain these results. First, in Japan, insurers have been required to provide AHCs to insured employees aged 40 to 74 under the Japanese National Health Screening and Intervention Program since 2008. Employees classified as having MetS are requested to receive intensive health guidance from health professionals, which includes a follow-up consultation for 3–6 months [Conversely, pre-MetS, considered a transitional pathway to MetS, showed a significant inverse association with PA level, presenting approximately 40% lower odds of reaching the daily recommended PA level than the no-MetS group. This finding indicates that participants with pre-MetS had significantly lower PA levels than those with no MetS, and were unlikely to achieve the current PA guidelines. A notable difference between the MetS and the pre-MetS groups may be whether individuals are receiving active health support with follow-up consultation. As the pre-MetS group exhibited significantly lowest odds among the MetS groups, those with pre-MetS would benefit from increased guidance to prevent the onset of MetS. Furthermore, we also found a significant association between pre-MetS and PA level only after adjusting for health awareness in addition to lifestyle factors. This finding suggests that health awareness is an important covariate for the association between MetS and PA.Given the non-significant associations between MetS and PA level, our results were inconsistent with previous studies that reported a clear inverse association between PA and MetS. However, it should be noted that the design of the present study differed from that of previous studies in that it examined the main exposure of MetS according to three categories and adjusted for a different selection of covariates. A study by Ko et al., which examined the association between PA and MetS in male white collar workers [When measuring PA in free-living conditions, the use of wearable devices may avoid recall bias by participants. However, that proprietary algorithms are not disclosed leaves a level of uncertainty [Another explanation for our results could be that activity levels differ between weekdays and weekends/holidays. We conducted a sensitivity analysis with the hypothesis that the day of the week could be an effect modifier for the association between MetS status and PA level. Indeed, we found that the interaction between the day of the week and MetS status was highly significant for both step count and active minutes. Thus, the fact that the study period included several days over the New Year’s holidays could have contributed substantially if PA differed according to the day of the week.