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Background: Low body mass index (BMI) is associated with chronic obstructive pulmonary disease (COPD) in populations where many are overweight. Substantial uncertainty remains about the relationship in populations with lower mean BMI levels, and about the relevance to it of the effects of smoking or of reverse causality.Methods: A nationally representative prospective cohort study included 221,194 Chinese men aged 40-79 years in 1990-91, who were followed up for 15 years or to the age of 80 years. Hazard ratios for COPD-related mortality vs baseline BMI were adjusted for age, smoking, drinking and other factors. To reduce reverse causality, main analyses excluded all men with prior history of any respiratory diseases or abnormal lung function at baseline, leaving 2960 COPD-related deaths (16% of all deaths).Results: The mean baseline BMI was 21.7 kg/m(2). There was a highly significant inverse association between BMI and COPD-related mortality among men without any apparent impairment of lung function. Approximately 90% of men had a baseline BMI <25 kg/m(2), and among them, 5 kg/m(2) lower BMI was associated with 31% (95% confidence interval 18-45%) higher COPD-related mortality. The excess risk persisted after restricting the analysis to never-smokers or excluding the first 5 years of follow-up.Conclusions: Low BMI is associated with increased COPD mortality in a relatively lean adult male population in China where COPD is one of the most common causes of death. [ABSTRACT FROM AUTHOR]

Background Vital registration of causes of death in China is incomplete with poor coverage of medical certification. Information on the leading causes of mortality will continue to rely on verbal autopsy (VA) methods. A new international VA form is being considered for data collection in China, but it first needs to be validated to determine its operating characteristics.Methods Detailed medical records and clinical evidence for 3290 deaths (mostly adults) among residents of six cities representative of the urban Chinese population were reviewed by a panel of physicians and coded by experts to establish a reference underlying cause of death. Independently, families of the deceased were interviewed using a structured symptomatic questionnaire and a separate death certificate was prepared for each matching case (2102). Validity of the VA procedure was assessed using standard measurement criteria of sensitivity, specificity, and positive predictive value.Results VA methods perform reasonably well in identifying deaths from several leading causes of adult deaths including stroke, several major cancer sites (lung, liver, stomach, oesophagus, and colorectal), and transport accidents. Sensitivity was less satisfactory in detecting deaths from several causes of major public health concern in China including ischaemic heart disease, chronic obstructive pulmonary disease, diabetes, and tuberculosis, and was particularly poor in diagnosing deaths from viral hepatitis, hypertension, and kidney diseases.Conclusions VA is an imprecise tool for detecting leading causes of death among adults. However, much of the misclassification generally occurs within broad cause groups (e.g. CVD, respiratory diseases, and liver diseases). Moreover, compensating patterns of misclassification would appear to suggest that, in urban China at least, the method yields population-level cause-specific estimates that are reasonably reliable. These results suggest the possible utility of these methods in rural China, to back up the low coverage of medical certification of cause of death owing to poor access to health facilities there. [ABSTRACT FROM AUTHOR]

Background Increased body mass index (BMI) is known to be related to ischaemic heart disease (IHD) in populations where many are overweight (BMI ≥ 25 kg/m2) or obese (BMI ≥ 30). Substantial uncertainty remains, however, about the relationship between BMI and IHD in populations with lower BMI levels.Methods We examined the data from a population-based, prospective cohort study of 222 000 Chinese men aged 40–79. Relative and absolute risks of death from IHD by baseline BMI were calculated, standardized for age, smoking, and other potential confounding factors.Results The mean baseline BMI was 21.7 kg/m2, and 1942 IHD deaths were recorded during 10 years of follow-up (6.5% of all such deaths). Among men without prior vascular diseases at baseline, there was a J-shaped association between BMI and IHD mortality. Above 20 kg/m2 there was a positive association of BMI with risk, with each 2 kg/m2 higher in usual BMI associated with 12% (95% CI 6–19%, 2P = 0.0001) higher IHD mortality. Below this BMI range, however, the association appeared to be reversed, with risk ratios of 1.00, 1.09, and 1.15, respectively, for men with BMI 20–21.9, 18–19.9, and <18 kg/m2. The excess IHD risk observed at low BMI levels persisted after restricting analysis to never smokers or excluding the first 3 years of follow-up, and became about twice as great after allowing for blood pressure.Conclusions Lower BMI is associated with lower IHD risk among people in the so-called normal range of BMI values (20–25 kg/m2), but below that range the association may well be reversed. [ABSTRACT FROM AUTHOR]

Background In China, tobacco smoking accounts for approximately 800 000 deaths annually and evidence suggests that tobacco use is rising. To improve tobacco control initiatives directed at youth, we conducted a population-based survey of children ages 11–20 years, both in and out of school. While there have been previous school-based studies on smoking prevalence and smoking-related knowledge, attitudes, and behaviours among adolescents in China, including the Global Youth Tobacco Survey, this survey also describes smoking behaviour among non-student youth. This population is important as approximately 40% of Chinese youths aged 15–19 years have already discontinued their studies.Methods A survey of smoking behaviour and smoking-related knowledge and attitudes was administered to 24 000 youths (students and non-students of middle school age) in 24 disease surveillance points in China, selected to include equal numbers of urban and rural children.Results The prevalence rates of experimenting were 47.8% for boys and 12.8% for girls. The prevalence of regular smoking among non-students was higher (8.3%) compared with students (5.2%). The strongest predictor of regular smoking was peer influence with 44% reporting that they obtained their first cigarette from peers. The majority of youths were aware that smoking was a cause of several diseases and addictive; however, non-students were less aware than students.Conclusions The evidence highlights the need for tobacco control interventions aimed at youths in China including non-student youths. For males, prevention programmes should extend into young adulthood. [ABSTRACT FROM AUTHOR]

Background National vital registration systems are the principal source of cause specific mortality statistics, and require periodic validation to guide use of their outputs for health policy and programme purposes, and epidemiological research. We report results from a validation of cause of death statistics from health facilities in urban China. Methods 2917 deaths from health facilities located in six cities in China constituted the study sample. A reference diagnosis of the underlying cause was derived for each death, based on expert review of available medical records, and compared with that filed at registration. Sensitivity, specificity and positive predictive value were computed for specific causes/cause categories according to the International Classification of Diseases (ICD), including analyses based on quality of evidence scores for each cause. Patterns of misclassification by the registration system were studied for individual causes of death. Results The registration system had good sensitivity in diagnosing cerebrovascular disease and several site specific cancers (lung, liver, stomach, colorectal, breast and pancreas). Sensitivity was average (50–75%) for some major causes of adult death in China, namely ischaemic heart disease (IHD), chronic obstructive lung disease (COPD), diabetes, and liver and kidney diseases, with compensatory misclassification patterns observed between several of them. Sensitivity was particularly low for hypertensive disease. Conclusions Although diagnostic misclassification is not uncommon in urban death registration data, they appear to balance each other at the population level. Compensating misclassification errors suggest that caution is required when drawing conclusions about particular chronic causes of adult death in China. Investment is required to improve the quality of cause attribution for health facility deaths, and to assess the validity of cause attribution for home deaths. Periodic assessments of the quality of cause of death statistics will enhance their usability for health policy and epidemiological research. [ABSTRACT FROM AUTHOR]