Tai Hing Lam

Body-mass index and all-cause mortality: Individual-participant-data meta-analysis of 239 prospective studies in four continents.

Summary Background Overweight and obesity are increasing worldwide. To help assess their relevance to mortality in different populations we conducted individual-participant data meta-analyses of prospective studies of body-mass index (BMI), limiting confounding and reverse causality by restricting analyses to never-smokers and excluding pre-existing disease and the first 5 years of follow-up. Methods Of 10u2008625u2008411 participants in Asia, Australia and New Zealand, Europe, and North America from 239 prospective studies (median follow-up 13·7 years, IQR 11·4–14·7), 3u2008951u2008455 people in 189 studies were never-smokers without chronic diseases at recruitment who survived 5 years, of whom 385u2008879 died. The primary analyses are of these deaths, and study, age, and sex adjusted hazard ratios (HRs), relative to BMI 22·5–<25·0 kg/m2. Findings All-cause mortality was minimal at 20·0–25·0 kg/m2 (HR 1·00, 95% CI 0·98–1·02 for BMI 20·0–<22·5 kg/m2; 1·00, 0·99–1·01 for BMI 22·5–<25·0 kg/m2), and increased significantly both just below this range (1·13, 1·09–1·17 for BMI 18·5–<20·0 kg/m2; 1·51, 1·43–1·59 for BMI 15·0–<18·5) and throughout the overweight range (1·07, 1·07–1·08 for BMI 25·0–<27·5 kg/m2; 1·20, 1·18–1·22 for BMI 27·5–<30·0 kg/m2). The HR for obesity grade 1 (BMI 30·0–<35·0 kg/m2) was 1·45, 95% CI 1·41–1·48; the HR for obesity grade 2 (35·0–<40·0 kg/m2) was 1·94, 1·87–2·01; and the HR for obesity grade 3 (40·0–<60·0 kg/m2) was 2·76, 2·60–2·92. For BMI over 25·0 kg/m2, mortality increased approximately log-linearly with BMI; the HR per 5 kg/m2 units higher BMI was 1·39 (1·34–1·43) in Europe, 1·29 (1·26–1·32) in North America, 1·39 (1·34–1·44) in east Asia, and 1·31 (1·27–1·35) in Australia and New Zealand. This HR per 5 kg/m2 units higher BMI (for BMI over 25 kg/m2) was greater in younger than older people (1·52, 95% CI 1·47–1·56, for BMI measured at 35–49 years vs 1·21, 1·17–1·25, for BMI measured at 70–89 years; pheterogeneity<0·0001), greater in men than women (1·51, 1·46–1·56, vs 1·30, 1·26–1·33; pheterogeneity<0·0001), but similar in studies with self-reported and measured BMI. Interpretation The associations of both overweight and obesity with higher all-cause mortality were broadly consistent in four continents. This finding supports strategies to combat the entire spectrum of excess adiposity in many populations. Funding UK Medical Research Council, British Heart Foundation, National Institute for Health Research, US National Institutes of Health.

Waist to stature ratio is more strongly associated with cardiovascular risk factors than other simple anthropometric indices

PURPOSEnTo determine which is the best anthropometric index among body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and waist to stature ratio (WSR) in relation to cardiovascular risk factors.nnnMETHODSnA representative sample of 2895 Hong Kong Chinese aged 25 to 74 years received medical examinations in 1995 and 1996. Anthropometric indices and cardiovascular risk factors in blood were measured, and partial correlation and Receiver Operator Characteristic (ROC) curves were used in analysis.nnnRESULTSnAmong 11 cardiovascular risk factors in partial correlation analysis, including ties WSR had the highest r in 6 in men, and 5 in women; followed by WC with 4 in men and 6 in women. In ROC analyses of 21 risk factors and health conditions, the area under curve (AUC) of WSR was the largest for most (13 of 21) factors in men and 10 in women; followed by WHR with 14 in women but only 5 in men. The optimal WSR cutoff value was 0.48 for both men and women.nnnCONCLUSIONSnWSR is the best simple anthropometric index in predicting a wide range of cardiovascular risk factors and related health conditions. A simple message that ones waist circumference should not exceed half the stature is recommended for the public.

Passive smoking exposure and risk of COPD among adults in China: the Guangzhou Biobank Cohort Study

BACKGROUNDnChronic obstructive pulmonary disease (COPD) is a leading cause of mortality in China, where the population is also exposed to high levels of passive smoking, yet little information exists on the effects of such exposure on COPD. We examined the relation between passive smoking and COPD and respiratory symptoms in an adult Chinese population.nnnMETHODSnWe used baseline data from the Guangzhou Biobank Cohort Study. Of 20 430 men and women over the age of 50 recruited in 2003-06, 15,379 never smokers (6497 with valid spirometry) were included in this cross-sectional analysis. We measured passive smoking exposure at home and work by two self-reported measures (density and duration of exposure). Diagnosis of COPD was based on spirometry and defined according to the GOLD guidelines.nnnFINDINGSnThere was an association between risk of COPD and self-reported exposure to passive smoking at home and work (adjusted odds ratio 1.48, 95% CI 1.18-1.85 for high level exposure; equivalent to 40 h a week for more than 5 years). There were significant associations between reported respiratory symptoms and increasing passive smoking exposure (1.16, 1.07-1.25 for any symptom).nnnINTERPRETATIONnExposure to passive smoking is associated with an increased prevalence of COPD and respiratory symptoms. If this association is causal, we estimate that 1.9 million excess deaths from COPD among never smokers could be attributable to passive smoking in the current population in China. Our findings provide strong evidence for urgent measures against passive smoking in China.

Mortality and smoking in Hong Kong : case-control study of all adult deaths in 1998

Abstract Objective: To assess the mortality currently associated with smoking in Hong Kong, and, since cigarette consumption reached its peak 20 years earlier in Hong Kong than in mainland China, to predict mortality in China 20 years hence. Design: Case-control study. Past smoking habits of all Chinese adults in Hong Kong who died in 1998 (cases) were sought from those registering the death. Setting: All the death registries in Hong Kong. Participants: 27 507 dead cases (81% of all registered deaths) and 13 054 live controls aged ≥35 years. Main outcome measures: Mortality from all causes and from specific causes. Results: In men aged 35-69 the adjusted risk ratios (and 95% confidence intervals) comparing smokers with non-smokers were 1.92 (1.70 to 2.16) for all deaths, 2.22 (1.94 to 2.55) for neoplastic deaths, 2.60 (2.10 to 3.21) for respiratory deaths (including tuberculosis, risk ratio 2.54), and 1.68 (1.43 to 1.97) for vascular deaths (each P<0.0001). In women aged 35-69 the corresponding risk ratios were 1.62 (1.40 to 1.88) for all deaths, 1.60 (1.33 to 1.93) for neoplastic deaths, 3.13 (2.21 to 4.44) for respiratory deaths, and 1.55 (1.20 to 1.99) for vascular deaths (each P<0.001). If these associations with smoking are largely or wholly causal then, among all registered deaths at ages 35-69 in 1998, tobacco caused about 33% (2534/7588) of all male deaths and 5% (169/3341) of all female deaths (hence 25% of all deaths at these ages). At older ages tobacco seemed to be the cause of 15% (3017/20 420) of all deaths. Conclusions: Among middle aged men the proportion of deaths caused by smoking is more than twice as big in Hong Kong now (33%) as in mainland China 10 years earlier. This supports predictions of a large increase in tobacco attributable mortality in China as a whole. What is already known on this topic China, with 20% of the worlds population, smokes 30% of the worlds cigarettes. Men smoke most, and the proportion of male deaths at ages 35-69 attributable to tobacco has been predicted to rise over the next few decades from 13% (in 1988) to about 33% In Hong Kong cigarette consumption reached its peak 20 years earlier than in mainland China, so the epidemic of male deaths from tobacco should now be at a more advanced stage What this study adds In the general population of Hong Kong in 1998 tobacco caused about 33% of all male deaths at ages 35-69 plus 5% of all female deaths, and hence 25% of all deaths at these ages In the male smokers tobacco caused about half of all deaths at ages 35-69 The hazards now seen in Hong Kong foreshadow a substantial increase in tobacco deaths among middle aged men in mainland China over the next few decades if current smoking patterns persist

Diabetic Control and Risk of Tuberculosis: A Cohort Study

Diabetes mellitus is associated with tuberculosis. A cohort of 42,116 clients aged 65 years or more, enrolled at 18 Elderly Health Service centers in Hong Kong in 2000, were followed up prospectively through the territory-wide tuberculosis registry for development of tuberculosis from 3 months after enrollment to December 31, 2005, by use of their identity card numbers as unique identifier. The effects of diabetes mellitus and diabetic control on tuberculosis risk were assessed with adjustment for sociodemographic and other background variables. Diabetes mellitus was associated with a modest increase in the risk of active, culture-confirmed, and pulmonary (with or without extrapulmonary involvement) but not extrapulmonary (with or without pulmonary involvement) tuberculosis, with adjusted hazard ratios of 1.77 (95% confidence interval: 1.41, 2.24), 1.91 (95% confidence interval: 1.45, 2.52), 1.89 (95% confidence interval: 1.48, 2.42), and 1.00 (95% confidence interval: 0.54, 1.86), respectively. Diabetic subjects with hemoglobin A1c <7% at enrollment were not at increased risk. Among diabetic subjects, higher risks of active, culture-confirmed, and pulmonary but not extrapulmonary tuberculosis were observed with baseline hemoglobin A1c > or =7% (vs. <7%), with adjusted hazard ratios of 3.11 (95% confidence interval: 1.63, 5.92), 3.08 (95% confidence interval: 1.44, 6.57), 3.63 (95% confidence interval: 1.79, 7.33), and 0.77 (95% confidence interval: 0.18, 3.35), respectively.

Hypertension: its prevalence and population-attributable fraction for mortality from cardiovascular disease in the Asia-Pacific region.

Objective About half of the worlds burden of cardiovascular disease is carried by countries in the Asia-Pacific region. This study aimed to quantify the contribution of hypertension to cardiovascular diseases (CVD) at the country level, by calculating the sex-specific, population-attributable fractions (PAFs) for fatal ischaemic heart disease (IHD) and stroke (haemorrhagic and ischaemic) for the World Health Organization Western Pacific and South-east Asian regions. Methods The most recent sex-specific prevalence data on hypertension were sought. Age-adjusted hazard ratio (HR) estimates for fatal IHD and stroke associated with hypertension were obtained using Cox analyses of individual participant cohort data from 600 000 adult participants in the Asia-Pacific Cohort Studies Collaboration. HR estimates and prevalence were then used to calculate sex-specific PAFs for fatal IHD and stroke, by country. Results In 15 countries with available data, the prevalence of hypertension ranged from 5–47% in men and from 7–38% in women. Overall, the fraction of IHD attributable to hypertension ranged from 4–28% in men and from 8–39% in women. Corresponding ranges for haemorrhagic stroke were 18–66% and 15–49%, and for ischaemic stroke were 8–44% and 12–45%. Conclusions In the Asia-Pacific region, up to 66% of some subtypes of CVD can be attributed to hypertension, underscoring the immense impact that blood pressure- lowering strategies could have in this populous region.

Adherence to nicotine replacement therapy versus quitting smoking among Chinese smokers: a preliminary investigation

RationaleThere are over 300 million Chinese smokers, but use of nicotine replacement therapy (NRT) is rare. On the other hand, data on the factors associated with quitting and adherence to NRT use are scarce in the East.ObjectivesTo describe adherence and other predictors of quitting smoking at the 12-month follow-up amongst Chinese smokers in Hong Kong.MethodsChinese smokers (1186) who attended the Smoking Cessation Health Centre from August 2000 through January 2002 were studied. Trained counsellors provided individual counselling and carried out follow-up interviews. We used structured questionnaires at baseline and at 1, 3 and 12 months and an intention-to-treat approach for analysis.ResultsAmong those who received NRT (1051/1186), the prevalence of adherence (self-reported NRT use for at least 4 weeks) was 16% (95% confidence interval 14–18%). The 7-day point prevalence quit rate at 12 months (not smoking any cigarette during the past 7 days at the 12 month follow-up) was 27% (95% CI, CI 24–29%). Stepwise logistic regression model showed that adherence to NRT use, a higher income, good perceived health and having more confidence in quitting were significant predictors of quitting. The quit rate in the adherent group (40%) was greater than that of the non-adherent group (25%) (P<0.001). Older age, male, higher education, experience of NRT use, perceiving quitting as more difficult and willingness to pay were significant predictors of adherence.ConclusionsClinically significant smoking cessation rates can be achieved among Chinese smokers in a clinic-based smoking cessation service. The NRT adherence was low and low adherence was associated with a lower quit rate. Trials of interventions to improve adherence and increase quit rates are needed.

Health-related physical fitness and weight status in Hong Kong adolescents

BackgroundThis study was designed to investigate the relation between health-related physical fitness and weight status in Hong Kong adolescents.Methods3,204 students aged 12-18 years participated in the Hong Kong Student Obesity Surveillance (HKSOS) project in 2006-2007. Anthropometric measures (height, weight) and health-related fitness (push-up, sit-up, sit-and-reach, 9-minute run) were assessed. Body mass index (BMI) was computed to classify participants into normal weight, underweight (Grade I, II/III), overweight, and obese groups. The associations of health-related physical fitness with BMI and weight status were examined by partial correlation coefficients and analysis of covariance, respectively.ResultsMore boys than girls were overweight or obese (18.0% vs 8.7%), but more girls than boys were underweight (22.3% vs 16.7%). Boys performed significantly (P < 0.001) better in sit-up (38.8 vs 31.6 times/min) and 9-minute run (1632.1 vs 1353.2 m), but poorer in sit-and-reach (27.4 vs 32.2 cm) than girls. All four physical fitness tests were significantly positively correlated with each other in both sexes, and BMI was only weakly correlated with sit up and sit-and-reach tests in boys. Decreasing performance (P for trend < 0.05) was observed from normal weight to overweight and obese for push-up, sit-up, and 9-minute run in both sexes. From normal weight to Grade I and Grade II/III underweight, decreasing performance (P for trend < 0.05) for sit-up and sit-and-reach in both sexes and for push-up in boys was observed.ConclusionsThe relations between BMI and health-related physical fitness in adolescents were non-linear. Overweight/obese and underweight adolescents had poorer performance in push-up and sit-up tests than normal weight adolescents. Different aspects of health-related physical fitness may serve as immediate indicators of potential health risks for underweight and overweight adolescents.

Passive Smoking and Tuberculosis

BACKGROUNDnIncreasing evidence has incriminated active smoking as a causal factor for tuberculosis (TB). However, the effect of secondhand tobacco smoke exposure on TB has not been similarly elucidated.nnnMETHODSnA cohort of 15 486 female never-smokers aged 65 to 74 years and living with their surviving husband were enrolled at 18 Elderly Health Centers in Hong Kong from 2000 to 2003 and followed up prospectively through linkage with the territory-wide TB notification registry and death registry for TB and death until December 31, 2008, using an identity card number as a unique identifier. The relationship between passive smoking and the development of TB was assessed with adjustment for other baseline characteristics.nnnRESULTSnPassive exposure to secondhand tobacco smoke in the household was independently associated with obstructive lung disease (odds [OR], 1.43; 95% confidence interval [CI], 1.16-1.77) and diabetes mellitus (OR, 1.13; 95% CI, 1.02-1.26) at baseline and with the development of both active TB (hazard ratio [HR], 1.49; 95% CI, 1.01-2.19) and culture-confirmed TB (HR, 1.70; 95% CI, 1.04-2.80) on prospective follow-up after potentially confounding background variables were controlled for. Passive smoking accounted for 13.7% of active TB and for 18.5% of culture-positive TB in this cohort.nnnCONCLUSIONSnSimilar to active smoking, passive exposure to secondhand tobacco smoke in the household also predisposes to the development of TB. Increased emphasis should therefore be put on tobacco control in national TB programs.

Age of menarche and the metabolic syndrome in China.

Objectives: In western populations, young age of menarche is associated with increased cardiovascular risk. Little is known about the potential impact of menarche on the metabolic syndrome (as a proxy for cardiovascular risk) in rapidly economically developing populations where age of menarche is falling. We sought to determine the relation between age of menarche and the metabolic syndrome in a rapidly developing Chinese population. Methods: We carried out a retrospective historical cohort study of 7349 women from the Guangzhou Biobank Cohort Study, China, enrolled in 2003–2004. Cardiovascular risk factors were obtained from physical examination; age of menarche was obtained from self-report. The main outcome measure was the metabolic syndrome and its components. Results: Adjusted for age, education, and number of pregnancies, young age of menarche (<12.5 years) compared with age of menarche ≥14.5 years was associated with a higher risk of the metabolic syndrome (odds ratio = 1.49; 95% confidence interval = 1.22–1.82), central obesity (1.35; 1.10–1.65), raised blood pressure (1.34; 1.09–1.65), raised fasting glucose (1.40; 1.15–1.71), and higher triglyceride levels (1.36; 1.12–1.67). Further adjustment by waist circumference attenuated these effects, but the odds ratios remained elevated. Conclusions: Earlier age of menarche experienced by younger women in China today, now 12.5 years on average in urban populations, may contribute to an increase in the metabolic syndrome and thereby an increase in cardiovascular disease as these women age. These results further highlight the importance of childhood antecedents of adulthood disease.