Table 1 shows the demographic characteristics of participants in the three surveys. The final sample sizes were 49, 233 in the 2002 survey (16, 828 in urban areas; 32, 405 in rural areas), 106, 673 in the 2010 survey (54, 016 in urban areas; 52, 657 in rural areas), and 179, 728 (73, 443 in urban areas; 106, 285 in rural area) in the 2015 survey. No statistical difference in genders was found among the three surveys.
Table 1. Demographic Characteristic Information of Participants in 2002, 2010, and 2015
In the 2002 survey, the mean age was 45.3 years (47.4 years in urban areas; 44.2 years in rural areas). Participants of Han descent accounted for 90.0% of the population (94.7% of the population in urban areas; 87.6% of the population in rural areas). Most participants completed junior or senior high school in urban areas; in rural areas, 50.2% of the participants attended primary school or below and only 2.6% had gone to college or above. The annual income of most participants was below 5, 000 RMB (44.7% in urban areas; 85.3% in rural areas).
The mean age in the 2010 survey was 52.0 years (50.5 years in urban areas; 52.3 years in rural areas) while that in the 2015 survey was 52.2 years (52.3 years in urban areas; 52.1 years in rural areas). An increasing trend of age was observed in the three surveys (P < 0.001). The number of participants with higher education levels and annual income significantly increased over the years (P < 0.001).
The total proportion of smokers was 26.6% (24.3% in urban areas; 27.7% in rural areas) in 2002, but no trend of smoking was observed among the three surveys. A significant decreasing trend of total proportion of drinkers from 22.3% in 2002 (23.1% in urban areas; 21.9% in rural areas) to 24.5% in 2010 (23.6% in urban area; 25.5% in rural areas) and then to 19.2% in 2015 (17.7% in urban areas; 20.0% in rural areas) (P < 0.001) was noted. By contrast, mean BMI showed a significant increasing trend from 23.2 kg/m2 in 2002 to 23.9 kg/m2 in 2010 and then to 24.2 kg/m2 in 2015 (P < 0.001). The proportions of low body weight (< 18.5 kg/m2), normal weight (18.5-23.9 kg/m2), overweight (24.0-27.9 kg/m2), and obese (≥ 28.0 kg/m2) participants significantly differed among the surveys (P < 0.001). Although the number of participants who had taken lipid control measures significantly increased from 2.4% in 2002 to 4.6% in 2010 and then to 4.5 in 2015 (P < 0.001), the overall proportion was still very low.
The trends of weighted adjustment Measurement of lipid control of lipid profiles among Chinese adults are demonstrated in Table 2. Total mean TC level and their 95% CIs significantly increased from 3.93 (3.87-3.99) mmol/L in 2002 to 4.59 (4.54-4.63) mmol/L in 2010 and then to 4.63 (4.59-4.67) mmol/L in 2015 (P < 0.001). Mean TG levels and their 95% CIs also significantly increased from 1.12 (1.10-1.15) mmol/L to 1.41 (1.39-1.44) mmol/L and then to 1.47 (1.45-1.50) mmol/L. However, mean HDL-c levels and their 95% CIs significantly decreased from 1.30 (1.28-1.31) mmol/L to 1.18 (1.16-1.20) mmol/L and then to 1.26 (1.24-1.27) mmol/L. Mean LDL-c levels and 95% CIs significantly increased from 2.12 (2.08-2.17) mmol/L to 2.78 (2.75-2.82) mmol/L and then to 2.87 (2.84-2.90) mmol/L (P < 0.001). Between the 2002 and 2010 surveys, mean levels of lipids, such as TC, TG and LDL-c, were higher in urban areas than in rural areas, but HDL-c concentrations were similar. However, in the 2015 surveys, TG and LDL-c levels were higher in urban areas than in rural areas; moreover, TC levels between urban and rural areas differed but HDL-c levels were higher in rural areas than in urban area. TG levels were much higher in males than in females in all three surveys. Increasing trends of TC, TG, and LDL-c levels were observed in males from 2002 to 2015; in females, the change in HDL-c was not significant. TC, TG, and LDL-c levels almost increased significantly with increasing age; in the 75-year-old group, a slight fluctuation of HDL-c level with no significant difference was observed during the period. Longitudinally, regardless of area, gender, or BMI, TC, TG, and LDL-c levels consistently increased whereas HDL-c levels decreased from 2002 to 2015 (P < 0.001). Weighted adjusted means of non-HDL-c levels in Table 3 showed an increasing trend in all age groups and both genders. An increasing trend of mean non-HDL-c levels was observed in urban and rural areas from 2002 to 2015. Similarly, the ratios of TC/HDL-c, TG/HDL-c, and LDL-c/HDL-c showed increasing trends among all genders, districts, ages, and BMIs (P < 0.001).
Table 2. Lipids Profiles among Participants in Survey 2002, 2010, and 2015 [mean (95% CI)]
Table 3. Non-HDL-c and Lipid-related Ratios among Participants in Survey 2002, 2010, and 2015 [mean (95% CI)]
Figure 2 shows the prevalence of dyslipidemia among Chinese adults from 2002 to 2015. The total weighted adjusted prevalence of hypercholesterolemia was 1.6% (95% CI: 1.3%-1.8%) in 2002, increased to 5.6% (95% CI: 5.1%-6.1%) in 2010, and then increased to 5.8% (95% CI: 5.3%-6.3%) in 2015 (P for trend < 0.001). Hypertriglyceridemia prevalence dramatically increased from 5.7% (95% CI: 5.1%-6.3%) to 13.6% (95% CI: 12.9%-14.2%) and then to 15.0% (95% CI: 14.3%-15.7%). Low HDL-c prevalence changed remarkably over these years, increasing from 18.8% (95% CI: 17.0%-20.6%) to 35.5% (95% CI: 33.3%-37.6%) and then to 24.9% (95% CI: 23.5%-26.4%). Similarly, LDL-c prevalence increased from 1.3% to 5.6% and then to 7.2% over the 13-year interval. Among urban and rural participants, the prevalence of hypercholesterolemia were much higher in the former than in the latter in the 2002 and 2010 surveys; however, in 2015, hypercholesterolemia prevalence was slightly higher in rural areas than in urban areas. Furthermore, in 2002, hypercholesterolemia prevalence was higher in females than in males, and it increased from 0.7% in the 18-year-old group to 3.4% in the 65-year-old group but then decreased to 2.7% in the 75-year-old group. Similar distributions of hypercholesterolemia were observed in the 2010 and 2015 surveys. From a longitudinal perspective, the prevalence of hypercholesterolemia from 2002 to 2015 remarkably increased in rural areas from 1.0% to 4.4% and then to 6.2%; interestingly, however, this prevalence in urban areas increased from 2.0% to 6.3% but then declined to 5.3%. About high LDL-c similar results with hypercholesterolemia was observed in both urban and rural areas, as well as in all genders, age groups, and BMI groups. However, hypertriglyceridemia prevalence was higher in males than in females, higher in urban areas than in rural areas, and higher in middle-aged adults than in their elderly counterparts. Longitudinally, an increasing trend of hypertriglyceridemia prevalence could be observed from 2002 to 2015. Low HDL-c prevalence was much higher in the dyslipidemia type. Moreover, HDL-c prevalence was higher in rural areas than in urban areas in 2002, while this prevalence was similar between areas in 2010 and then higher in urban areas than in rural areas in 2015. Interestingly, in the age groups of 55 years and above, the trends of low HDL-c prevalence were not statistically significant among the three survey years.