Risk factors in V‐shaped risk associations with all‐cause mortality in type 2 diabetes—The Hong Kong Diabetes Registry

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Abstract
Background Body mass index (BMI) is associated with death in a V-shaped manner in general populations but it is unknown whether BMI or other risk factors also exhibit V-shaped relationships with death in type 2 diabetic patients. Methods A prospective cohort of 7534 Chinese, type 2 diabetic patients enrolled since 1995 were censored on 30 July 2005. Spline Cox regression analysis with a stepwise algorithm (p < 0.05) was used to select predictors. Hazard ratio (HR) curves were used to explore the relationships, which were confirmed by standard Cox models. Results 763 patients died during the 5.5 years of follow-up. BMI, high-density lipoprotein cholesterol (HDL-C) and white blood cell (WBC) count were related to all-cause mortality in a V-shaped manner. The nadirs of the risk curves were at 26 kg/m2 for BMI, 1.15 mmol/L for HDL-C and 6.25 × 109 counts/L for WBC. The multivariate hazard ratio of BMI away from 26.0 kg/m2 was 1.08; HDL-C, 1.06 per mmol/L for values less than the nadir and 6.97 per mmol/L for greater than the nadir; and WBC, 1.16 per 109 count/L for less than 6.25 × 109 and 1.47 for greater than the nadir. Respiratory and neoplastic deaths were the major contributors to the increased death in patients with low or high BMI. Neoplastic death was the major contributor to the increased death in those with low WBC. Genitourinary death was the major contributor to the increased death in those with low and high HDL-C. Conclusion BMI, HDL-C and WBC are associated with death in a V-shaped manner in type 2 diabetic patients. Copyright © 2007 John Wiley & Sons, Ltd.