A prospective study of impaired fasting glucose and type 2 diabetes in China: The Kailuan study

Abstract

The worldwide prevalence and incidence of diabetes and obesity are increasing in pandemic proportions. This is particularly relevant for China, where an extremely large population is growing, aging, and urbanizing. We thus conducted a prospective study to examine the prevalence and incidence of impaired fasting glucose (IFG) and diabetes, the rate at which fasting blood glucose rises, and the major modifiable risk factors associated with these outcomes in a large Chinese population from the Kailuan prospective study.A prospective cohort included 100,279 Chinese participants, aged 18 years or more, who had available information on fasting blood glucose concentrations at the start of the study (2006). Examination surveys were conducted every 2 years in 2008 and 2010. For the analyses of incident diabetes, we included 76,869 participants who were free of diabetes, cardiovascular disease, and cancer at the baseline and participants in the 2008 and/or 2010 follow-up. Diabetes was defined by a fasting blood glucose concentration ≥7 mmol/L, self-reported history, or active treatment with insulin or any oral hypoglycemic agent. IFG was defined by a fasting blood glucose concentration between 5.6 and 6.9 mmol/L.During the 4-year study, the prevalence of diabetes and IFG rose from 6.6% to 7.7%, and 17.3% to 22.6%, respectively. There were 17,811 incident cases of IFG and 4867 incident cases of diabetes. The age-standardized incident rate of IFG and diabetes were 62.6/1000 person-years (51.2/1000 person-years in women and 73.8/1000 person-years in men) and 10.0/1000 person-years (7.8/1000 person-years in women and 12.1/1000 person-years in men), respectively. We observed steady increases in fasting blood glucose with body anthropometrics and in every defined category of body mass index, including in those traditionally considered to be well within the "normal" range.In this large longitudinal study of Chinese adults, we observed a high prevalence and incidence of IFG and diabetes over 4 years of follow-up. Our findings are alarming for Chinese public health since steady rises in fasting blood glucose were seen across all permutations of body habitus, even apparently very lean individuals.

Figure 1

Incident rate (per 1000 person-year) of diabetes (panel A) and impaired fasting glucose (panel B) according to gender and baseline age in 2006. ^∗P < 0.05, ^∗∗P < 0.001, relative to women.

Figure 2

Change in fasting blood glucose concentrations between surveys according to baseline body mass index (BMI) among men (panel A) and women (panel B) without diabetes at the baseline. The interaction term of BMI with time was significant (P < 0.0001) for both men and women, suggesting that higher BMI was associated with a significantly faster increase in glucose over time.

Figure 3

Hazard ratio of diabetes (panel A: men and B: women) and impaired fasting glucose (panel C: men and D: women) according to the joint classification of body mass index and waist circumference in men and women, adjusting for age (y), education (illiteracy/primary, high school or college, or above), working environment (working on the ground, underground, not exposure to dust, or underground, exposure to dust), family history of diabetes (yes/no), smoking (never, past smoker, current smoker 1–19 cigarettes/d, or current smoker 20+ cigarettes/d), alcohol drinking (never, past drinker, current drinker <1 time/d, or current drinker 1+ times/d), hypertension (yes/no), and fasting plasma glucose (mmol/L).