Differences in the prevalence of metabolic syndrome by company size in Japan

Introduction
In 2008, specific health examinations and guidance for metabolic syndrome (MetS) were launched in Japan to prevent morbidity and mortality from cardiovascular disease. Some studies have reported that workers in small and medium-scale enterprises showed a higher frequency of abnormal findings. This study investigated differences in the prevalence of MetS according to company size and discussed how to improve occupational health in the workplace.

Methods
The subjects were 26,234 workers (male: 9,277; female: 16,957) aged 40-74 who underwent a specific health check-up from 305 workplaces in DEPARTMENTSTORE HEALTH INSURANCE in Tokyo. MetS and pre-MetS were judged by Japanese criteria including waist circumference (male ≥85 cm and female ≥90 cm), systolic or diastolic blood pressure ≥130/85mmHg, triglyceride ≥150mg/dl or HDL cholesterol<40mg/dl, fasting blood glucose ≥110mg/dl and medication. Each workplace <300 employees was classified as small-scale enterprises (SSEs), 300-899 employees as 300-scale enterprises (300SEs), 900-2999 employees as 900-scale enterprises (900SEs), or >3000 employees as large-scale enterprise (LSEs).

Results
The frequencies of MetS and pre-MetS were 5.9% and 2.8% in LSEs, 9.6% and 7.9% in 900SEs, 9.3% and 8.9% 300SEs, and 10.0% and 8.9% in SSEs respectively. Compared with LSEs, a higher percentage of combined MetS and pre-Mets showed OR: 1.77 (95%CI: 1.54 to 2.03) in 900SEs, OR: 1.86(1.61 to 2.13), and OR: 1.82 (1.57 to 2.10) in SSEs after adjusting for gender and age. P for trend (<0.0001) was shown among these four scales of enterprises.

Discussion
Workers in SSEs and MSEs would be considered to have worse lifestyles and working environments, such as longer work hours and higher levels of stress. These findings suggest that workers showed higher frequencies of Mets and pre-MetS in SSEs and MSEs. Therefore, it is very important to strengthen and improve workplace health promotion in SSEs and MSEs.