In the present study, the population studied presents a high prevalence of co-PreHTN and PreDM in apparently healthy Chinese adults. The prevalence of co-PreHTN and PreDM was even higher in men than women, and increased with age and BMI. Our findings suggest that prevalence of co-PreHTN and PreDM in our population is similar to that observed in a recent survey conducted in a healthy US population . It has been previously reported that PreDM markedly increases CVD risk in prehypertensive individuals . The recent findings of the Strong Heart Study also revealed that in non-diabetic individuals, IFG and PreHTN increases the number of cardiovascular events by 2.06-fold compared to their normotensive and normoglycemic counterparts, with an absolute increase of 5 cardiovascular events per 1000 person years .
It has also been previously shown that there are marked ethnic and geographic differences in BP and FBG levels in China [9, 17]. Living conditions, habitual diets, and social circumstances in disparate communities also exhibit different characteristics. In the present study, the prevalence of co-PreHTN and PreDM was higher in the Hei Longjiang province of northern China compared to the Inner Mongolian Autonomous Region in northeastern China (13.3% versus 8.8%). There are a number of potential factors that may contribute to these differences. For example, there are more people in the Hei Longjiang province that are overweight or obese, dyslipidemic, and have a higher salt intake . Unfortunately, data on dietary sodium intake were not collected in the present study. Furthermore, based on the regional differences, there may be genetic contributions to the co-PreHTN and PreDM phenotype that should also be considered.
There was a higher prevalence of co-PreHTN and PreDM among individuals that consumed alcohol and smoked. This finding was consistent with earlier studies, which found that excessive alcohol consumption and cigarette smoking increase BP and glucose levels [19, 20]. Interestingly, we also found that there was higher prevalence of ex-smokers than current smokers in the co-PreHTN and PreDM group. This observation can be explained by the findings of Inoue K , who suggested that the adverse effects associated with the weight gain following cessation of smoking outweigh the benefits. Weight gain is a strong risk factor for CVD, which is also closely associated with a substantial risk for impaired glucose regulation and elevated BP .
In the present study, we also observed that, with the exception of HDL-C, the lipid profile and glucose levels demonstrated a gradual upward trend from the normotensive and normoglycemic group, followed by the co-PreHTN and PreDM group, and lastly the hypertensive and diabetic group. In addition to the larger WC and BMI, our findings also suggest that these considerably "healthy" men and women are at an increased risk for CVD. Other biochemical parameters, such as GGT and UA levels, were also relatively higher in subjects with co-PreHTN and PreDM. Recent cross-sectional and longitudinal studies have also noted a relatively independent association between elevated serum GGT levels, and hypertension and diabetes [23, 24]. We have also revealed that higher serum GGT levels are positively associated with PreHTN in an otherwise healthy Chinese adult population following various adjustments in the multivariate logistic regression analysis (unpublished observations). In addition, a recent study  found that elevated GGT was independently associated with the presence of the IFG, further supporting our conclusion. Similarly, serum UA levels correlated with metabolic abnormalities and CVD . A previous study found that there is a significant association between serum UA levels and the risk of PreHTN. Meanwhile, in the Rancho Bernardo Study, it was suggested that UA may be a useful predictor of type 2 diabetes in older adults with IFG . However, the underlying mechanisms for higher GGT and UA in subjects with co-PreHTN and PreDM are unclear and require further clarification.
A major strength of our study is that it is a population-based study with a good representative sample of the general Chinese population. Additionally, the larger sample size ensures sufficient power in estimating the prevalence of co-PreHTN and PreDM, as well as determining the correlation between co-PreHTN and PreDM, and CVD risk factors. Lastly, the use of standardized protocols and instruments guaranteed a high response rate and excellent quality control.
However, the study also has several limitations. First, oral glucose tolerance test (OGTT) was not performed in subjects with IFG, thereby potentially reducing the accurate diagnosis of diabetes. Since some individuals with normal FBG may have IGT, based on OGTT data, examining FBG alone (i.e. without a 2-h PBG) may result in the underestimating of the prevalence of co-PreHTN and PreDM in healthy Chinese adults. Lastly, the study is based on a cross-sectional survey, which is unable to determine causality or the temporal relationship between CVD risk factors and co-PreHTN and PreDM.