Changes in smoking behavior and subsequent mortality risk during a 35-year follow-up of a cohort in Xi'an, China.

Prospective evidence of the associations of smoking cessation with chronic obstructive pulmonary disease (COPD) and other causes of death in Asia is scarce. Previous studies, which were mostly based on baseline smoking behavior only, were subject to sick-quitter bias and misclassification resulting from changes in smoking behavior during follow-up. We followed up a cohort for 18 years (1976-1994) to assess changes in smoking behavior and then for an additional 17 years (1994-2011) to examine the relationships of continuing to smoke and new quitting with mortality risk in 1,494 Chinese people (961 men, 533 women). Of the baseline current smokers, 38.7% quit between 1976 and 1994. From 1994 to 2011, a total of 488 persons (359 men, 129 women) died. Ever smokers had increased risks of lung cancer, coronary heart disease, thrombotic stroke, and COPD, with dose-response relationships. For all tobacco-related mortality, the relative risk for new quitters compared with continuing smokers was 0.68 (95% confidence interval: 0.46, 0.99) for those who had quit 2-7 years previously and 0.56 (95% confidence interval: 0.37, 0.85) for those who had quit 8 years or more previously. The corresponding relative risks were 0.69 and 0.45 for lung cancer, 0.78 and 0.51 for coronary heart disease, 0.76 and 0.84 for thrombotic stroke, and 0.89 and 0.61 for COPD, respectively. Smoking increased tobacco-related deaths, and particularly deaths from COPD, in China, whereas quitting at middle age (at approximately 50 years of age) substantially reduced the risks of death from these causes. The benefits of smoking cessation were underestimated in previous studies that did not use repeated measures.

Secondhand smoke exposure predicted COPD and other tobacco-related mortality in a 17-year cohort study in China.

BACKGROUND: Prospective evidence on the association between secondhand smoke (SHS) and COPD and ischemic stroke is scarce. METHODS: We prospectively examined the relationship between SHS and major tobacco-related deaths, particularly COPD and stroke, in 910 Chinese (439 men, 471 women) who never smoked from a 17-year follow-up study in Xi'an, China. SHS exposure was defi ned as exposure to another person's tobacco smoke at home or in the workplace. RESULTS: At baseline among the 910 subjects, 44.2% were exposed to SHS at home, 52.9% in the workplace, and 67.1% at home, work, or both. From March 1, 1994, to July 1, 2011, 249 (150 men,99 women) died within 14,016 person-years. Those who were exposed to SHS had increased mortality due to coronary heart disease (adjusted relative risk [RR], 2.15; 95% CI, 1.00-4.61), ischemic stroke (RR, 2.88; 95% CI, 1.10-7.55), lung cancer (RR, 2.00; 95% CI, 0.62-6.40), COPD (RR, 2.30;95% CI, 1.06-5.00), and all causes (RR, 1.72; 95% CI, 1.29-2.20), with significant dose-response relationships between cumulative SHS exposure at home and work and the increased risk of cause-specific and total mortality (P for linear trend ranged from .045 to , .001). CONCLUSIONS: This study shows dose-response relationships between SHS and major tobacco-related mortality and provides new evidence to support causation for COPD and ischemic stroke.

Triglyceride and coronary heart disease mortality in a 24-year follow-up study in Xi'an, China.

PURPOSE: To study whether serum triglyceride (TG) was associated with coronary heart disease (CHD) mortality. METHODS: A cohort analytic study carried out in a machinery factory in Xi'an, China on 1696 subjects aged 35 years or above (1124 men and 572 women) examined in 1976 and followed up till 2000. RESULTS: At baseline, the mean serum total cholesterol (TC) and triglyceride (TG) was 4.64 and 1.16 mmol/L in men, 4.62 and 1.10 mmol/L in women, respectively. Three hundred six (239 men, 67 women) had died within 37,781 person-years of follow-up, with 49 CHD deaths (36 male, 13 female). The relative risk (95% confidence interval) of CHD mortality per mmol/L increase in TG was 2.13 (1.46-3.17) after adjusting for age, marital status, occupation, education, systolic blood pressure and TC. Dose-response relationship between TG levels by tertiles and CHD risk was found. Stratified analyses showed TG was an independent predictor for CHD mortality in subjects with lower or higher TC. CONCLUSIONS: Chinese had lower levels of TC and TG than Western populations. This study provides new evidence that TG is an independent risk factor of CHD in subjects with lower or higher TC levels, and supports the lowering of cut-off value for elevated triglyceride.