Liu et al. BMC Public Health 2011, 11:931 http://www.biomedcentral.com/1471-2458/11/931 Page 6 of 9 Table 4 Factors associated with systolic blood pressure and changes in systolic blood pressure by gender and occupation among cohort populations in Guangzhou, China, 1983-1994 Males Females Workers Farmers Workers Farmers SE 0.5 0.1 0.5 3.5 0.1 0.1 0.4 0.5 SE 1.2 0.1 1.3 0.4 0.3 0.9 1.1 **P < 0.01; *P < 0.05; aFour education levels: never attended school, primary school, middle school, and high school or higher; bNot included in the model because few females smoked; and c13.7 g/d is equivalent to 1 drink/d medication usage indicate that SBP in hypertensive per- sons was far from being control. Baseline BMI was significantly and directly associated with SBP, and increase in BMI was significantly asso- ciated with increase in SBP in every gender-occupation group (Table 4). Although cigarette smoking was inver- sely associated with average SBP, increase in the amount of smoking was associated with increase in SBP among males. Baseline alcohol intake was significantly and directly associated with SBP among males. Except among male farmers, change in the amount of drinking was not associated with change in SBP. Overall, the results of GEE analyses for DBP were similar to those of SBP. Factors associated with serum lipids and changes in serum lipids Table 5 presents the results of GEE analyses for TC. Except among female workers, the regression coefficient of time was statistically significant, indicating a signifi- cant increase in TC over time. Baseline BMI was directly related to average TC and increase in BMI was related to increase in TC among all four groups. Cigar- ette smoking was not significantly related to average TC, but increase in the amount of smoking was directly related to increase in TC among male farmers. Among males, baseline alcohol intake was directly related to average TC and increase in the amount of intake was positively related to increase in TC. For other lipid measures, i.e., LDL-C, HDL-C, and trigly- cerides, the multivariate-adjusted regression coefficients of time were statistically significant among most gender- occupation groups (except LDL-C in female workers and triglycerides in either female workers or female farmers) (data not shown). The associations between baseline BMI and the three lipid measures were all statistically signifi- cant (directly for LDL-C, triglycerides; and inversely for HDL-C) among every gender-occupation group. Likewise, Table 5 Factors associated with serum total cholesterol and changes in serum total cholesterol by gender and occupation among cohort populations in Guangzhou, China, 1983-1994 Males Females Workers Farmers Workers Farmers **P < 0.01; *P < 0.05; aFour education levels: never attended school, primary school, middle school, and high school or higher; bNot included in the model because few females smoked; and c13.7 g/d is equivalent to 1 drink/d Time (10 years) Age (year) Education (levela) Antihypertensive medication use Body mass index (kg/m2) Change in body mass index (kg/m2) Cigarettes per day (10/d) Change in cigarettes per day (10/d) Alcohol intake (13.7 g/dc) Change in alcohol intake (13.7 g/dc) Time (10 years) Age (year) Education (levela) Body mass index (kg/m2) Change in body mass index (kg/m2) Cigarettes per day (10/d) Change in cigarettes per day (10/d) Alcohol intake (13.7 g/d) Change in alcohol intake (13.7 g/d) b 4.1** 0.7** -0.2 13.1** 1.5** 1.1** b b -0.7 0.2 SE 0.7 0.1 0.4 1.7 0.1 0.2 0.7 1.0 b 2.0 1.8** 0.9 1.2** 1.3** b b 1.8 0.9 SE 1.5 0.1 0.8 0.3 0.4 2.2 1.1 b 2.7** 0.5** -0.01 17.3** 0.6** 1.0** b b -1.0 0.9 b 13.2** 1.2** 4.3** 1.5** 1.8** b b -0.1 0.7 b 3.0** 0.4** -0.7* 13.8** 1.5** 1.5** -1.6** 0.7* 0.5** -0.3 b 5.4** 0.8** 3.4** 1.4** 2.3** -0.2 -0.6 1.3** 0.6* SE 0.7 0.1 0.4 1.9 0.1 0.2 0.3 0.4 0.2 0.2 SE 1.4 0.1 1.0 0.4 0.5 0.8 0.6 0.5 0.3 b 5.5** 0.2** 0.2 15.9** 1.0** 1.5** -1.2** 0.8* 0.3** -0.4** b 19.4** -0.1 1.4 1.4** 3.1** 0.6 1.0* 0.9** 0.4* SE 0.7 0.1 0.6 3.1 0.2 0.3 0.2 0.3 0.1 0.1 SE 1.6 0.1 1.6 0.4 0.6 0.6 0.5 0.2 0.2