Low high‐density lipoprotein cholesterol level is a significant risk factor for development of type 2 diabetes: Data from the Hawaii–Los Angeles–Hiroshima study

AIMS/INTRODUCTION A low level of high-density lipoprotein cholesterol (HDLC) is a common feature of metabolic syndrome. We have reported that Japanese-Americans who share a virtually identical genetic makeup with native Japanese, but who have lived Westernized lifestyles for decades, have lower HDLC levels and a high prevalence of type 2 diabetes compared with native Japanese. However, the impact of low HDLC level on type 2 diabetes is unclear. The aims of the present study were to evaluate whether serum HDLC level was associated with development of type 2 diabetes and if the effect might be modified by lifestyle. MATERIALS AND METHODS We examined 1,133 non-diabetic Japanese-Americans and 1,072 non-diabetic Japanese, who underwent the 75-g oral glucose tolerance test (OGTT) and were followed for an average of 8.8 and 7.0 years, respectively. We analyzed whether serum HDLC level is a risk factor for development of type 2 diabetes based on the Cox proportional hazards model. RESULTS After adjustment for age and sex, hazard ratios for development of type 2 diabetes per unit of serum HDLC level (mmol/L) were 0.292 (95% confidence interval [CI] 0.186-0.458, P < 0.0001) among Japanese-Americans and 0.551 (95% CI 0.375-0.88, P = 0.0023) among native Japanese. Comparable hazard ratios after further adjustment for category of OGTT and body mass index were 0.981 (95% CI 0.970-0.993, P = 0.0018) and 0.991 (95% CI 0.980-1.002, P = 0.112), respectively. CONCLUSIONS HDLC level was associated with development of type 2 diabetes in both Japanese-Americans and native Japanese. However, these results suggest that the impact of high-density lipoprotein on glucose metabolism might be affected by lifestyle.