Associations of risk factors clustering with the risk of cardiovascular disease and their population attributable fraction in a worksite cohort study in urban to suburban Japan

Abstract

Objective: A health examination program targeting metabolic syndrome criteria, which includes abdominal obesity as a mandatory condition has been implemented to prevent cardiovascular diseases (CVD) in Japan. However, even non-obese individuals with risk factors are reportedly at a similarly increased risk of CVD. Since this group represents more in Japan than those meeting the aforementioned criteria, there is still a need to assess risk and population impact of risk factor accumulation in non-obese individuals to inform public health policy. Also, whether CVD risks according to the risk factor accumulation differ by the presence of obesity was mostly examined in community settings, leaving necessity for studies in urban employees, who may have different lifestyles and higher rates of coronary artery disease. This study aimed to estimate CVD risks and population-attributable fractions (PAFs) by the number of CVD risk factors, stratified by obesity status, in a cohort of local government employees.

Methods: This study included 7,179 participants from the Aichi Workers' Cohort Study recruited between 2002-2008 without histories of CVD and cancer or missing data at baseline and followed-up for at least one year. The participants were categorized into four groups (0, 1, 2, or ≥3) according to the number of the following risk factors: hypertension, diabetes, high LDL cholesterol, kidney disease and, smoking, which were further divided by obesity status. Multivariable-adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and the 95% confidence intervals (CIs) as well as PAFs for CVD incidence.

Results: During follow-up, 99 developed CVD (66 non-obese and 33 obese). Among non-obese participants, compared to those with no risk factors, the HR for CVD incidence increased with the number of risk factors: 2.43 (95%CI: 1.14-5.21), 3.96 (95%CI: 1.79-8.74), and 4.75 (95%CI: 1.73-13.0) for one, two and three or more risk factors, respectively. In the obese group, the HRs compared to non-obese individuals with no risk factors increased similarly according to the number of risk factors: 4.31 (95%CI: 1.85-10.00), 3.75 (95%CI: 1.47-9.57), and 7.53 (95%CI: 2.86-19.8) for one, two, and three or more risk factors, respectively. The PAFs were 16.7%, 16.6%, and 5.6% in the non-obese group and 10.9%, 6.7%, and 7.0% in the obese group for one, two, and three or more risk factors, respectively.

Conclusion: Accumulation of risk factors was associated with increased CVD risk regardless of obesity status.