Liu et al. BMC Public Health 2011, 11:931 http://www.biomedcentral.com/1471-2458/11/931 Page 4 of 9 Table 1 Baseline characteristics by gender and occupation among cohort populations in Guangzhou, China, 1983-1984 Males Females Workers Mean or % SD Age (years) 42.1 8.7 Education (%) Never school 2.1 Primary school 36.8 Middle school 35.7 High school or above 25.4 Current smoker (%) 71.7 Cigarettes per day Total 12.7 11.8 Current smoker 17.7 10.3 Current alcohol drinker (%) 24.9 Alcohol intake (g/per day) Total 10.6 28.9 Drinker 42.4 44.8 Systolic blood pressure (mmHg) 115.0 14.8 Diastolic blood pressure (mmHg) 74.6 9.8 Hypertension (%) 9.7 Taking antihypertensive medication (%) Total 1.3 Hypertensive 13.8 Body mass index (kg/m2) 20.5 2.4 Weight category (%) Normal 95.3 Overweight 4.7 Obesity 0.0 Total cholesterol (mg/dl) 181.9 32.0 Low density cholesterol (mg/dl) 112.2 28.4 High density cholesterol (mg/dl) 49.6 12.1 Triglycerides (mg/dl) 104.9 86.4 *P < 0.01 comparing workers and farmers within the same gender Farmers Mean or % 42.4 * 8.3 75.3 14.1 2.3 81.8* 18.6* 22.7* 61.0* 51.8* 84.9* 115.5 72.3* 7.4* 0.3* 3.6* 19.9* * 99.1 0.9 0.1 158.6* 94.0* 49.1 80.8* SD 8.9 14.8 13.2 74.0 78.5 14.0 9.5 1.9 30.3 25.3 12.2 77.6 Workers Mean or % 41.1 11.5 34.3 25.0 29.2 2.8 0.2 8.4 1.8 0.4 20.4 114.4 74.0 10.5 1.3 12.1 21.4 88.3 10.8 1.0 187.2 114.5 53.4 100.3 SD 8.2 1.8 7.2 4.5 27.4 17.2 10.5 3.0 33.2 29.2 12.4 90.5 Farmers Mean or % 41.7 * 57.4 40.4 1.8 0.5 5.3* 0.5* 9.7 7.7* 1.3* 17.3 109.8* 68.8* 3.8* 0.3* 6.7 19.7* * 98.9 1.0 0.1 155.4* 92.4* 47.9* 76.1* SD 9.6 2.9 8.2 7.3 20.5 13.9 9.1 2.0 28.7 25.0 10.4 44.0 low at follow-ups (e.g., 13.4% among male workers, 6.8% among male farmers, 18.4% among female workers, and 6.0% among female farmers at year 10), these represented significant increases above baseline. Likewise, age- adjusted prevalence of hyperlipidemia increased signifi- cantly in the four gender-occupation groups (except female workers). We calculated the age-adjusted average 10-year change of risk factor levels (continuous variables) by the GEE method (Table 3). Average SBP and DBP increased signifi- cantly in all four groups with the biggest increase among male farmers. BMI also increased significantly and the big- gest increase (1.4 kg/m2 in 10 years) was among farmers. Cigarette smoking and alcohol drinking were uncommon in females. Average TC and LDL-C increased significantly, especially among farmers. High density lipoprotein choles- terol (HDL-C) changed little in workers but significantly increases in farmers. Average triglycerides markedly increased among male workers and male farmers. Factors associated with blood pressure and changes in blood pressure Table 4 presents the results of the GEE analyses examin- ing the independent longitudinal changes of SBP, factors associated with SBP, and changes of factors associated with change in SBP. The positive coefficients of time indicate that average SBP increased significantly in 10 years after adjustment for aging of the cohorts and other factors (including the changes of the factors) in the mod- els. The large coefficients of the antihypertensive