Hin-Peng Lee

Singapore Chinese Health Study: development, validation, and calibration of the quantitative food frequency questionnaire.

This report describes the development and validation/calibration of a structured food frequency questionnaire for use in a large-scale cohort study of diet and health in Chinese men and women aged 45-74 years in Singapore, the development of a food composition database for analysis of the dietary data, and the results of the dietary validation/calibration study. The present calibration study comparing estimated intakes from 24-hour recalls with those from the food frequency questionnaires revealed correlations of 0.24-0.79 for energy and nutrients among the Singapore Chinese, which are comparable to the correlation coefficients reported in calibration studies of other populations. We also report on the nutritional profiles of Singapore Chinese on the basis of results of 1,880 24-hour dietary recalls conducted on 1,022 (425 men and 597 women) cohort subjects. Comparisons with age-adjusted corresponding values for US whites and blacks show distinct differences in dietary intakes between the Singapore and US populations. The Singapore cohort will be followed prospectively to identify dietary associations with cancer risk and other health outcomes.

New ISSCR Guidelines Underscore Major Principles for Responsible Translational Stem Cell Research

The International Society for Stem Cell Research (ISSCR) task force that developed new Guidelines for the Clinical Translation of Stem Cells discusses core principles that should guide the responsible transition of basic stem cell research into appropriate clinical applications.

Risk factors for breast cancer by age and menopausal status: a case-control study in Singapore.

A case-control study was conducted among Singapore Chinese women, comprised of 200 histologically confirmed cases of breast cancer and 420 hospital controls. Subjects were interviewed on family history of breast cancer, social and demographic characteristics, reproductive history, and diet one year prior to interview. Differences in risk factors were observed according to menopausal status. In the premenopausal group, the most consistently significant nondietary effect was an increased risk with late age at first birth. In postmenopausal women, the most consistent nondietary effects were increased risks with nulliparity, tall stature, high educational status, and a family history of breast cancer. In premenopausal women, the strongest dietary effects were low risks with high intakes of polyunsaturated fatty acids (PUFA), β-carotene, soya protein as a proportion of all protein, and a high risk with high red-meat intake. No dietary effects were observed in postmenopausal women. Examination of effects by 10-year age groups suggested that the differences in the effects of age at first birth, nulliparity, height, education, β-carotene intake, and PUFA intake between premenopausal and postmenopausal women were at least partly attributable to age-related differences in the baseline distributions of these variables. The variation in the effects of red meat and soya protein appeared to be attributable mainly to menopausal status itself, which is consistent with the hypothesis that these factors operate on risk by way of hormonal mechanisms.

Sleep Duration and Coronary Heart Disease Mortality Among Chinese Adults in Singapore: A Population-based Cohort Study

While some studies have found a positive association between both short and long sleep durations and cardiovascular disease (CVD), others have found an association only with a long or short sleep duration. In addition, there are limited data from non-Western populations on this topic. The authors examined the association between sleep duration and coronary heart disease (CHD) mortality among Chinese adults in Singapore (1993-2006), performing a prospective cohort study among 58,044 participants aged > or =45 years (55.9% women) without preexisting CVD. The main outcome of interest was CHD mortality (n = 1,416). The authors found both short and long sleep durations to be positively associated with CHD mortality, independent of smoking, alcohol intake, and body mass index. Compared with persons with a sleep duration of 7 hours (referent), the multivariable relative risk of CHD mortality for a sleep duration of < or =5 hours was 1.57 (95% confidence interval: 1.32, 1.88); for a sleep duration of > or =9 hours, it was 1.79 (95% confidence interval: 1.48, 2.17). This association persisted in subgroup analyses by sex and body mass index. In a population-based cohort of Chinese adults from Singapore, sleep durations of < or =5 hours and > or =9 hours (versus 7 hours) were modestly associated with CHD mortality. These results suggest that sleep duration may be an important marker for CVD.

Basal cell carcinoma, squamous cell carcinoma and melanoma of the skin: analysis of the Singapore Cancer Registry data 1968–97

Summary Background There has been an alarming recent increase in skin cancer incidence among fair‐skinned populations. Information from Asian populations is less readily available.

Sleep duration, melatonin and breast cancer among Chinese women in Singapore

BACKGROUND Sleep duration has been hypothesized to be inversely associated with breast cancer risk, possibly due to greater overall melatonin production in longer sleepers. However, data are inconclusive from the three studies conducted in Western populations on sleep duration and breast cancer risk. METHODS We investigated the relationship between self-reported usual sleep duration determined at baseline and subsequent risk of breast cancer in the prospective, population-based cohort of the Singapore Chinese Health Study. We excluded from the study women with <2 years of follow-up due to possible change in sleep pattern among breast cancer cases close to the time of diagnosis. Five hundred and twenty-five incident cases of breast cancer were identified among the remaining 33 528 women after up to 11 years of follow-up. RESULTS Among women postmenopausal at baseline, breast cancer risk decreased with increasing sleep duration (P trend = 0.047); those who reported 9+ h of sleep showed a relative risk of 0.67 (95% confidence interval = 0.4-1.1) compared with women who reported < or =6 h of sleep. This inverse association was observed primarily in lean women [i.e. body mass index below the median value (23.2 kg/m(2))] (P = 0.024). In this study population, irrespective of gender, urinary 6-sulfatoxymelatonin levels increased with increasing self-reported hours of sleep (P trend = 0.035) after adjustment for age and time of day of urine collection. Melatonin levels were 42% higher in those with 9+ versus those with < or =6 h of sleep. CONCLUSION Sleep duration may influence breast cancer risk, possibly via its effect on melatonin levels.

Diet, reproductive factors and lung cancer risk among Chinese women in Singapore: evidence for a protective effect of soy in nonsmokers.

The factors associated with risk of lung cancer among nonsmokers have not been fully elucidated, but dietary factors have consistently been shown to play a role. Chinese women are unique in having a high incidence of lung cancer despite a low smoking prevalence. This population is also known to have a high intake of soy, a dietary source of phytoestrogens. We conducted a hospital‐based case‐control study among Singapore Chinese women, comprising 303 cases and 765 age‐matched controls, of whom 176 cases and 663 controls were lifetime nonsmokers. Data on demographic background, reproductive factors and dietary intake of fruit, vegetables and soy foods were obtained by in‐person interview. We observed an inverse association between intake of total, cruciferous and non‐cruciferous vegetables and risk of lung cancer among smokers. Although smokers in the highest tertile of fruit intake also had a lower risk, this was not statistically significant. Higher intake of soy foods significantly reduced risk of lung cancer among lifetime nonsmokers, but not among smokers. When soy isoflavonoid intake in mg/week was computed based on frequency and portion size of intake of eight common local soy foods, the adjusted OR among nonsmokers for the highest tertile compared to the lowest was 0.56, 95% CI 0.37–0.85 (p for trend <0.01). Fruit intake was also significantly associated with reduced lung cancer risk among nonsmokers, but the effect was not significant after adjustment for soy intake. On the other hand, soy intake remained an independent predictor of risk after controlling for fruit intake. Reproductive effects were also primarily confined to lifetime nonsmokers, among whom having 3 or more livebirths (adjusted OR 0.65, 0.44–0.96) and a menstrual cycle length of more than 30 days (OR 0.46, 0.25–0.84) accorded a significantly reduced risk of lung cancer. Place of birth was significantly associated with risk among nonsmokers (OR 2.6, 1.7–3.9 for China‐born vs. local born) but not among smokers. When analysis was restricted to nonsmokers with adenocarcinomas, the dietary effects were consistent or enhanced. On stepwise regression, soy intake and cycle length emerged as the independent dietary and reproductive predictors of lung cancer risk in nonsmokers. These findings are consistent with other evidence suggesting an involvement of estrogen‐related pathways in lung cancer among non‐smoking women.

HSD17B1 and CYP17 polymorphisms and breast cancer risk among Chinese women in Singapore

Reasons for the recent trend of increasing breast cancer incidence among Chinese and other Asian women are not well understood. Endogenous estrogen levels are strongly associated with breast cancer risk and its determinants include both genetic and lifestyle factors. We conducted a nested case‐control study to investigate, within the Singapore Chinese Health Study Cohort, the relationships between polymorphisms in 2 genes involved in estrogen metabolism, CYP17 and HSD17B1, and the risk of breast cancer. For this analysis, 188 incident breast cancer cases and 671 female cohort control subjects were compared. When the HSD17B1 A allele was considered as the “putative high‐risk” allele, there was a modest increased risk (adjusted relative risk, RR=1.37, 95% CI=0.90–2.07 for HSD17B1 AA vs. other); this association was statistically significant in analysis restricted to postmenopausal women (RR=1.86, 95% CI=1.14–3.03). There was no significant association between the CYP17 MspAI polymorphism and risk in all subjects (RR=1.06, 95% CI=0.65–1.74 for CYP17 A2A2 vs. CYP17 A1A1) or in postmenopausal women only. When we evaluated breast cancer risk in relation to the joint stratification of CYP17 and HSD17B1 genotypes and according to the combined number of putative high‐risk alleles (range, 0–4), we observed an elevated joint effect of the CYP17 and HSD17B1 genes on risk. Women who possessed all 4 putative high‐risk alleles of both genes (CYP17 A2A2 and HSD17B1 AA) vs. less displayed a nearly 2‐fold increased risk (RR=1.83, 95% CI=0.97–3.44); this finding was statistically significant in postmenopausal women (RR=2.31, 95% CI=1.07–4.98). Risk of breast cancer was similar among women possessing the other genotypes (i.e., less than 4 putative high‐risk alleles in the joint CYP17/HSD17B1 genotypes). In addition, the significant increased risk of breast cancer associated with nulliparity or late age at first live birth (age 31 years or older) was largely limited to women with the high‐risk CYP17 A1A2/A2A2 or HSD17B1 AA genotypes (RR=2.41, 95% CI=1.56–3.72; RR=4.39, 95% CI=1.71–11.30, respectively). The latter gene‐parity effects were especially pronounced in postmenopausal women.

Childhood exposure to environmental tobacco smoke and chronic respiratory symptoms in non-smoking adults: The Singapore Chinese Health Study

Background: Childhood exposure to environmental tobacco smoke has been extensively associated with childhood respiratory illness; fewer studies have addressed the effects on adults. Methods: Childhood environmental tobacco smoke exposure in relation to chronic cough, phlegm, and asthma diagnosis was studied in never smokers from a cohort of Singaporeans of Chinese ethnicity aged 45–74 years at enrolment from 1993 to 1998. From 1999 to 2004 subjects were interviewed regarding environmental tobacco smoke exposure before and after the age of 18 and the presence and duration of current symptoms of chronic cough and phlegm production and asthma diagnosis. Results: Among 35 000 never smokers, fewer had smoking mothers (19%) than fathers (48%). Although few subjects currently lived (20%) or worked (4%) with smokers, 65% reported living with a daily smoker before the age of 18 years. Living with a smoker before the age of 18 increased the odds of chronic dry cough (149 cases, odds ratio 2.1, 95% CI 1.4 to 3.3) and, to a lesser extent, phlegm, after adjustment for age, sex, dialect group, and current and past exposure to smokers at home and at work after the age of 18. Associations strengthened with higher numbers of smokers in childhood. There was no association with asthma or chronic bronchitis. There was evidence to suggest a stronger association among subjects with a lower adult intake of fibre which has previously been found to be protective for respiratory symptoms. Conclusions: In this large study of non-smokers, living with a smoker in childhood was associated with chronic dry cough and phlegm in adulthood, independent of later exposures to environmental tobacco smoke.

A prospective study of tobacco and alcohol use as risk factors for pharyngeal carcinomas in Singapore Chinese

Nasopharyngeal carcinoma (NPC) is a rare disease in most populations; however, in areas of Southeast Asia and North Africa and in the Arctic, undifferentiated NPC is the most frequent pharyngeal malignancy. Although smoking and alcohol have been established firmly as synergistic risk factors for other pharyngeal carcinomas, previous studies on the association between these risk factors and NPC have not been consistent. Therefore, the authors analyzed this relation in a cohort of Singapore Chinese, which is a population with a high incidence of NPC.