Every 1,000 steps matter: incremental reductions in metabolic syndrome risk in Japanese office workers

Several studies have investigated the association between metabolic syndrome (MetS) and physical activity (PA). However, further research is needed using objective measures of PA in free-living conditions, while also accounting for the time-variant nature of MetS. This study aimed to: (1) investigate the association between wearable device-measured step count and 5-year MetS incidence in generally healthy Japanese participants, using annual health check-up (AHC) data and interval-censored survival analysis; and (2) assess the current, and recently revised, reference value (8,000 steps/day) of Japan's Ministry of Health, Labour and Welfare (MHLW), and (3) investigate the possibility of non-linear associations between daily step count and MetS.

This longitudinal prospective observation study identified average daily step count per year/person as the main exposure, and MetS incidence, defined according to Japanese guidelines, as the main outcome. The main analysis included 730 participants without MetS or pre-MetS at baseline. An interval-censored Cox model was applied to assess MetS incidence using time-to-event data.

Every 1,000 steps added to the average step count was significantly and inversely associated with incident MetS in adjusted models [Model 1: HR = 0.92; 95% CI: 0.85, 1.00; Model 2: HR = 0.91; 95% CI: 0.83, 0.99] (p < 0.05). The current reference value (8,000 steps/day) also indicated a significant inverse association [Model 1: HR = 0.32; 95% CI: 0.14, 0.71; Model 2: HR = 0.26; 95% CI: 0.11, 0.61] (p < 0.01). Higher daily step counts lowered the risk of MetS incidence according to the amount of steps up to a step count of 12,000, however, the dose-response effect was attenuated beyond 12,000 steps/day.

Each additional 1,000 daily steps was associated with a 9% reduction in the risk of developing MetS among healthy participants. The reference value (8,000 steps/day) was associated with a 74% reduction in MetS risk.