Cohort Profile: Hong Kong Department of Health Elderly Health Service Cohort.

The Department of Health Elderly Health Service Cohort in Hong Kong was set up to promote understanding of ageing in a global context, to exploit the role of Hong Kong as a sentinel for populations currently experiencing very rapid economic development, to provide a developed non-Western 'social laboratory' where empirically derived hypotheses can be tested and to leverage the different patterns of common chronic diseases between East and West to generate novel hypotheses about their determinants. The initial cohort enrolled from July 1998 to the end of December 2001 includes 66 820 people aged 65 years or older, forming about 9% of the population of this age. A comprehensive health assessment was made at enrollment and then repeated regularly on an ongoing basis. The health assessment included a comprehensive assessment of lifestyle, social circumstances, physical health and mental health, including an assessment of cognition and depressive symptoms. Health services use and deaths have been obtained by record linkage and confirmed, where necessary, by telephone interview. Currently, the data are not publicly available; we would welcome collaborations and research proposals.

Systematic differences among never, occasional and moderate alcohol users in southern China, and its use in alcohol research: a cross-sectional study.

BACKGROUND: Western observational studies show moderate alcohol use, compared with never use, positively associated with health. Moderate users differ systematically from others, making these observations vulnerable to confounding. Observations from other contexts may help distinguish whether these associations are confounded. To assess whether southern Chinese would provide a more suitable setting to examine the association of moderate alcohol use with health, we compared never alcohol users with moderate alcohol users and occasional users in this setting. METHODS: We used age-adjusted multinomial regression to assess sex-stratified associations of alcohol use (never, occasional (<1 occasion/week), moderate (≤140 g ethanol/week for women and ≤210 g for men)) with health attributes and indicators in the Guangzhou Biobank Cohort Study (2003-2008) (n=26 361). RESULTS: Among men, moderate alcohol users, when compared with never users, had slightly lower socioeconomic position and unhealthier lifestyle. Conversely, occasional alcohol users, when compared with never users, had higher socioeconomic position and healthier lifestyle. Among women, when compared with never users, both occasional and moderate users had higher socioeconomic position and healthier lifestyle. However, all alcohol users for both sexes, when compared with never users, were more likely to be ever smokers and to be exposed to secondhand smoke. CONCLUSIONS: Observations in alcohol epidemiology may be affected by confounding due to contextually specific systematic differences. Results from a particular setting should not be interpreted as causal unless they are verified in different populations and, preferably, in non-observational studies.

Are the 2006 World Health Organization standards for infant growth applicable to Hong Kong Chinese? Universalistic standards or epidemiological transition stage-specific norms.

1. Parental socio-economic status was positively associated with length and body mass index of Hong Kong Chinese infants at 9 months. 2. Maternal smoking in pregnancy was negatively associated with infant length at 9 months. 3. Some of the World Health Organization (WHO) criteria for an optimal nurturing environment contributed positively to growth. At 36 months, Hong Kong Chinese infants were generally shorter and fatter than the WHO growth references.

Patterns of and hypotheses for infection-related cancers in a Chinese population with rapid economic development.

With economic development, non-communicable diseases replace infectious diseases as the leading cause of death; how such transition occurs for infectious diseases with long latency has rarely been considered. We took advantage of a Chinese population with rapid economic development in the mid-20th century to study changing patterns of infection-related cancers. We used sex-specific Poisson regression to estimate age, period and cohort effects on adult deaths 1976-2005 from eight infection-related cancers in Hong Kong. Cervical, head and neck, and oesophageal cancers, associated with sexually transmitted infections, decreased for the first birth cohorts with sexual debut in a more developed environment. Leukaemia and non-Hodgkin's lymphoma, associated with vertically transmitted infections, decreased for the first cohorts born into a more developed environment. Birth cohort patterns were unclear for nasopharyngeal, stomach and liver cancers. Mortality rates for cancers related to early infections may depend on population history, with delayed reductions for some infection-related cancers.

Childhood meat eating and inflammatory markers: the Guangzhou Biobank Cohort Study.

BACKGROUND: We hypothesized that socio-economic development could, via nutritionally driven levels of pubertal sex-steroids, promote a pro-inflammatory state among men but not women in developing countries. We tested this hypothesis, using recalled childhood meat eating as a proxy for childhood nutrition, in southern China. METHODS: We used multivariable linear regression in the Guangzhou Biobank Cohort Study phase 3 (2006-8) to examine the adjusted associations of recalled childhood meat eating, <1/week (n = 5,023), about once per week (n = 3,592) and almost daily (n = 1,252), with white blood cell count and its differentials among older (≥ 50 years) men (n = 2,498) and women (n = 7,369). RESULTS: Adjusted for age, childhood socio-economic position, education and smoking, childhood meat eating had sex-specific associations with white blood cell count and lymphocyte count, but not granulocyte count. Men with childhood meat eating almost daily compared to <1/week had higher white blood cell count (0.33 109/L, 95% confidence interval (CI) 0.10 to 0.56) and higher lymphocyte count (0.16 109/L, 95% CI 0.07 to 0.25). Adjustment for obesity slightly attenuated these associations. CONCLUSION: If confirmed, this hypothesis implies that economic development and the associated improvements in nutrition at puberty may be less beneficial among men than women; consistent with the widening sex differentials in life expectancy with economic development.

Socioeconomic influences at different life stages on health in Guangzhou, China.

In long-term developed countries socioeconomic position across the life course is positively associated with health. We examined these associations in a developing country with a history of efforts to reorganize the social hierarchy. Taking a life course perspective, we used multi-variable logistic regression to assess the association of socioeconomic disadvantage at four life stages (measured by parental possessions, education, longest-held occupation and current household income) with self-rated health, chronic obstructive pulmonary disease (COPD) and metabolic syndrome in 20,086 Chinese adults aged ≥50 years from the Guangzhou Biobank Cohort Study (2005-2008). Model comparisons were used to determine whether the number of exposures to disadvantage (accumulation of risk) was more important than the life stage of exposure (critical periods). Socioeconomic disadvantage across the life course was associated with poor self-rated health, COPD and, in women only, with metabolic syndrome. Adjusting for adult health-related behavior (smoking, alcohol use and physical exercise) altered these associations very little. Associations between socioeconomic disadvantage and health in this Southern Chinese population were broadly similar to those found in Western countries in terms of the accumulation of disadvantage across the life course. However, longest-held occupation was not independently associated with adult health and socioeconomic disadvantage was not associated with metabolic syndrome in men. This suggests that the mechanisms linking socioeconomic position to health in China may be different from those in Western populations and may require context-specific policy interventions.

Leg length and age of puberty among men and women from a developing population: the Guangzhou Biobank Cohort study.

OBJECTIVES: Leg length and relative leg length are considered to be reliable markers of prepubertal living conditions. Cessation of leg growth, driven by estrogen, occurs earlier in puberty in girls than boys. We hypothesized that leg length and relative leg length, as sitting height to leg ratio, might have sex-specific associations with age of puberty. METHODS: We used multivariable linear regression in 10,046 older (>or=50 years) Chinese from the Guangzhou Biobank Cohort Study (Phase 3) to examine the associations of recalled age of puberty (women: age of menarche, and men: mean age of first nocturnal emission, voice breaking, and first pubic hair) with subischeal leg length, sitting height to leg ratio, and sitting height. RESULTS: Leg length and sitting height to leg ratio had different associations with age of puberty in men and women (P-values for interaction <0.001), but sitting height did not. Per year earlier puberty, legs were longer among men by 0.09 cm (95% confidence interval (CI) 0.01-0.18) and shorter among women by -0.16 cm (95% CI -0.20 to -0.12). Further adjustment for age, hip size (as a marker of buttock fat), and several markers of childhood conditions did not obviate the difference in association by sex. CONCLUSIONS: Adult leg length and relative leg length (sitting height to leg ratio) may be biomarkers of different exposures in men and women, with corresponding implications for their interpretation as a biomarker of early life exposures.

A socio-biological explanation for social disparities in non-communicable chronic diseases: the product of history?

This study places social disparities in the major non-communicable chronic diseases within their global economic and historical contexts. Rapid economic transition outside the developed world provides a unique opportunity to re-examine the origins of, and biological mechanisms driving, social disparities. Gaps in prevailing theories focusing on material resources, civic infrastructure and social structure are identified. Using longstanding experimental evidence and epigenetic theories, it is suggested that exposure to economic development over generations (ie, improved living conditions over historical time) could by acting on different biological axes (somatotrophic and gonadotrophic) generate specific patterns of social disparities. Moreover, these same processes could initially generate a transient epidemic of diabetes as well as a permanent increase in male risk of premature ischaemic heart disease. As such, this study demonstrates the importance of context, and implies that current evidence from the developed world may be largely uninformative for preventing or mitigating social disparities in non-communicable chronic diseases elsewhere, suggesting research efforts should be focused on developing countries.

A socio-historical hypothesis for the diabetes epidemic in Chinese--preliminary observations from Hong Kong as a natural experiment.

It has been hypothesized that the emerging epidemic of diabetes in economically transitioning or recently transitioned populations is due to mismatch between developmental and mature environments. We took advantage of migration within an ethnically homogenous population to investigate this hypothesis, and the potentially modifying role of postnatal growth conditions, proxied by greater height. We used multivariable logistic regression in a population-based cross-sectional study from 1994 to 1996 of 2,341 long-term Hong Kong residents aged 25-74 years, either born in contemporaneously developed Hong Kong or migrants from economically undeveloped Guangdong. Migrant status was not associated with clinically diagnosed diabetes, odds ratio 1.05 (95% confidence interval 0.69-1.58) in adult migrants compared to Hong Kong-born natives and 1.22 (0.83-1.80) in preadult migrants, adjusted for age, sex, socio-economic position, and lifestyle. However, the association of diabetes with migrant status varied with height, suggesting a potentially complex relationship between indicators of prenatal and postnatal nutritional exposures. Compared to tall Hong Kong-born natives, the odds ratio of diabetes was 2.36 (1.20-4.61) in tall migrants, 1.94 (1.07-3.53) in short Hong Kong-born natives, but 1.04 (0.48-2.23) in short adult migrants. Additionally adjusting for body mass index and waist-hip ratio had little effect, apart from attenuating the association between short height and diabetes prevalence in Hong Kong-born natives. Whether the current epidemic of diabetes is a long-standing effect of such mismatch or a "first-generation through effect" generated by rapid economic development causing disproportionate growth remains to be determined.

Are height and leg length universal markers of childhood conditions? The Guangzhou Biobank cohort study.

OBJECTIVE: In developed western populations longer legs have been shown to be a marker of better early childhood conditions. In the first generations to experience the epidemiologic transition and associated economic development, epigenetic constraints on growth might preclude improved childhood conditions from increasing leg growth or height. DESIGN, SETTING AND PARTICIPANTS: Multivariable linear regression was used to assess the association of parental growth environment, proxied by parental literacy, and childhood conditions, proxied by parental possessions, with leg length, sitting height and height in a cross-sectional sample from 2005-6 of 9998 Chinese people aged at least 50 years from phase 2 of the Guangzhou Biobank Cohort Study. MAIN RESULTS: Adjusted for age and sex, the association of childhood conditions with leg length and height varied with parental literacy (interaction p values <0.01 and 0.03), but not for sitting height (p value 0.43), with statistically significant trends (p values <0.01) for parental possessions to be associated with longer legs and greater height only in the offspring of two literate parents where legs were longer by 0.56 cm (95% CI 0.27 to 0.86) and height greater by 1.16 cm (95% CI 0.74 to 1.58) for participants with most, compared with least, parental possessions in childhood. CONCLUSIONS: Epigenetic influences originating in earlier generations may constrain growth during the infancy and/or childhood phases in very recently developed populations. Neither height nor leg length should be assumed to be consistent proxies of early life environment with corresponding implications for economic history, the aetiology of some chronic diseases and the monitoring of population health.

Is leg length a biomarker of childhood conditions in older Chinese women? The Guangzhou Biobank Cohort Study.

OBJECTIVE: In developed western populations longer legs have been shown to be a biomarker of better early childhood conditions. It was hypothesised that in transitioning populations better childhood conditions may bring forward puberty and thus decrease leg length, counteracting the overall positive effect of a favourable childhood environment on leg growth. DESIGN: Structural equation modelling was used to assess the interrelationship of age, education, father's job, age of menarche and leg length in a cross-sectional sample of 7273 Chinese women aged at least 50 years from the Guangzhou Biobank Cohort Study. RESULTS: Leg length had no significant association with education or father's occupation on bivariable testing. After including age of menarche in the model, education was associated with longer legs (0.45 cm longer per 10 years of education, 95% CI 0.20 to 0.71). Education was also associated with younger age of menarche (1.21 years younger per 10 years of education, 95% CI 1.09 to 1.34), which was in turn associated with shorter legs (0.23 cm shorter per year of menarche earlier, 95% CI 0.18 to 0.27). CONCLUSIONS: In older Chinese women leg length is not a universal biomarker of childhood conditions, when proxied by her educational level and father's occupation. Nutritionally driven epigenetic influences operating over generations may constrain growth in very recently developed populations. Given the impact of childhood conditions on health, and the dearth of long-term records outside the industrialised world, a greater understanding of the influences on growth in the developing world is required.

Are universal standards for optimal infant growth appropriate? Evidence from a Hong Kong Chinese birth cohort.

OBJECTIVE: In 2006 the World Health Organization (WHO) published new optimal growth standards for all healthy infants worldwide. To assess their general applicability to a recently transitioned Chinese population, we compared them with infant growth patterns in a representative sample of Hong Kong infants. DESIGN AND SETTINGS: Weight at birth and at 1, 3, 9, 12, 18 and 36 months, length at 3 and 9 months and height at 36 months were obtained for over 80% of all infants born in April and May 1997 (3880 boys and 3536 girls). Age and sex specific z scores were calculated relative to the WHO growth standards for term singletons. RESULTS: Weight for age was close to the 50th percentile of the WHO growth standards for both boys (mean z score: 0.00) and girls (0.04) at most time points before 3 years of age. However, our participants were shorter at 3 years, where the z scores in height were -0.34 and -0.38 for boys and girls, respectively. Restricting the analysis to a subset matching the WHO criteria for healthy infants without restrictions on growth gave similar results. CONCLUSIONS: Although the WHO study group concluded there was a striking similarity in length/height among different populations, Hong Kong Chinese toddlers are, on average, shorter. Epigenetic constraints on growth coupled with the rapid epidemiological transition in Hong Kong may not have allowed sufficient generations for infants and children to reach their full genetic height potential, and with it the WHO standards. A universal infant growth standard may not be appropriate across all populations.

Life-course origins of social inequalities in metabolic risk in the population of a developing country.

In countries that have been industrialized for a long time, but not always elsewhere, low socioeconomic position (SEP) is associated with ischemic heart disease in men. The authors hypothesized that socioeconomic development could, via pubertal sex steroids, promote an atherogenic lipid profile and body shape in men but not in women. Therefore, they examined the associations of SEP with ischemic heart disease risk in a developing-country population. The authors used multivariable regression to examine the associations of SEP with the metabolic syndrome and its components in 9,746 Chinese adults aged >/=50 years from the Guangzhou Biobank Cohort Study, phase 2, recruited in 2005-2006. After adjustment for age, smoking, alcohol use, and physical activity, high SEP at each of three life stages, proxied by parental possesions in childhood, education, and longest held-occupation, was inversely associated with the metabolic syndrome in women but not in men. Higher SEP in men was associated with lower pulse pressure and fasting plasma glucose level but also with greater waist circumference and a lower high density lipoprotein cholesterol level. With socioeconomic development, diet-related hormonal changes at puberty may outweigh the usual protective effect of social advantage in men, with corresponding implications for boys currently undergoing the nutrition transition in the developing world.

Age-period-cohort analysis of tuberculosis notifications in Hong Kong from 1961 to 2005.

BACKGROUND: Despite its wealth, excellent vital indices and robust health care infrastructure, Hong Kong has a relatively high incidence of tuberculosis (TB) (85.4 per 100 000). Hong Kong residents have also experienced a very rapid and recent epidemiological transition; the population largely originated from migration by southern Chinese in the mid 20th century. Given the potentially long latency period of TB infection, an investigation was undertaken to determine the extent to which TB incidence rates reflect the population history and the impact of public health interventions. METHODS: An age-period-cohort model was used to break down the Hong Kong TB notification rates from 1961 to 2005 into the effects of age, calendar period and birth cohort. RESULTS: Analysis by age showed a consistent pattern across all the cohorts by year of birth, with a peak in the relative risk of TB at 20-24 years of age. Analysis by year of birth showed an increase in the relative risk of TB from 1880 to 1900, stable risk until 1910, then a linear rate of decline from 1910 with an inflection point at 1990 for a steeper rate of decline. Period effects yielded only one inflection during the calendar years 1971-5. CONCLUSIONS: Economic development, social change and the World Health Organisation's short-course directly observed therapy (DOTS) strategy have contributed to TB control in Hong Kong. The linear cohort effect until 1990 suggests that a relatively high, but slowly falling, incidence of TB in Hong Kong will continue into the next few decades.