Smoking cessation and lung cancer risk in an Asian population: findings from the Singapore Chinese Health Study.

BACKGROUND: Smoking cessation is an important strategy for reducing the harmful effects of tobacco, particularly in the prevention of lung cancer; however, prospective data on the impact of smoking cessation on lung cancer risk in Asian populations are limited. METHODS: We studied a population-based cohort of Chinese men and women aged 45-74 years--participants of the Singapore Chinese Health Study. Information on smoking, lifestyle and dietary habits was collected at the time of recruitment in 1993-1998; and smoking status was assessed again at a second interview in 1999-2004 (mean interval 5.8 years). Participants were followed up to 31 December 2007, and incident cases of lung cancer were ascertained by linkage with population-wide registries. RESULTS: Among 45,900 participants, there were 463 incident cases of lung cancer. Relative to current smokers, those who quit smoking subsequent to baseline assessment had a 28% decrease in the risk of lung cancer (adjusted hazard ratio (HR) 0.72; 95% CI (95% confidence interval): 0.53-0.98). The risk was less than half in ex-smokers who had quit before the first interview and maintained their status (HR 0.42; 95% CI: 0.32-0.56). CONCLUSIONS: Reduction in lung cancer incidence with smoking cessation in Asian populations is substantial and can be observed within a few years after quitting.

Heterocyclic aromatic amines in domestically prepared chicken and fish from Singapore Chinese households.

Chicken and fish samples prepared by 42 Singapore Chinese in their homes were obtained. Researchers were present to collect data on raw sample weight, cooking time, maximum cooking surface temperature, and cooked sample weight. Each participant prepared one pan-fried fish sample and two pan-fried chicken samples, one marinated, one not marinated. The cooked samples were analyzed for five heterocyclic aromatic amine (HAA) mutagens, including MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline); 4,8-DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline); 7,8-DiMeIQx (2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline); PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), and IFP (2-amino-(1,6-dimethylfuro[3,2-e]imidazo[4,5-b])pyridine). A paired Student's t-test showed that marinated chicken had lower concentrations of PhIP (p<0.05), but higher concentrations of MeIQx (p<0.05) and 4,8-DiMeIQx (p<0.001) than non-marinated chicken, and also that weight loss due to cooking was less in marinated chicken than in non-marinated chicken (p<0.001). Interestingly, the maximum cooking surface temperature was higher for fish than for either marinated or non-marinated chicken (p<0.001), yet fish was lower in 4,8-DiMeIQx per gram than marinated or non-marinated chicken (p<0.001), lower in PhIP than non-marinated chicken (p<0.05), and lost less weight due to cooking than either marinated or non-marinated chicken (p<0.001). Fish was also lower in MeIQx and 7,8-DiMeIQx than marinated chicken (p<0.05). This study provides new information on HAA content in the Singapore Chinese diet.

Do urinary estrogen metabolites reflect the differences in breast cancer risk between Singapore Chinese and United States African-American and white women?

Breast cancer risk is substantially lower in Singapore than in women from the United STATES: Part of the risk discrepancy is probably explained by differences in the production of endogenous estrogens, but differences in the pathway by which estrogen is metabolized may also play a role. We undertook a study to determine whether the ratio of urinary 2-hydroxyestrone (2OHE(1)):16alpha-hydroxyestrone (16alpha-OHE(1)) was higher in Singapore Chinese than in a group of United States (predominantly African-American) women living in Los ANGELES: We also wanted to determine whether any difference in estrogen metabolite ratio between these two groups of women was greater than that in estrone (E(1)), estradiol (E(2)) and estriol (E(3)). The participants in this study were randomly selected healthy, non-estrogen using women participating in the Singapore Chinese Health Study (n = 67) or the Hawaii/Los Angeles Multiethnic Cohort Study (n = 58). After adjusting for age and age at menopause, mean urinary 2-OHE(1) was only 23% (P = 0.03) higher in Singapore Chinese than in United States women, and there were no statistically significant differences in 16alpha-OHE(1) levels or in the ratio of 2-OHE(1):16alpha-OHE(1) between the two groups. The adjusted mean 2-OHE(1):16alpha-OHE(1) ratio was 1.63 in Singapore Chinese and 1.48 in United States women (P = 0.41). In contrast, the adjusted mean values of E1, E2, and E3 were 162% (P < 0.0001), 152% (P < 0.0001), and 92% (P = 0.0009) higher, respectively, in United States women than in Singapore Chinese women. Our study suggests that urinary E1, E2, and E3 reflect the differences in breast cancer risk between Singapore Chinese and United States women to a stronger degree than the estrogen metabolites 2OHE(1) and 16alpha-OHE(1) or the ratio of 2OHE(1):16alpha-OHE(1.)

Potential sources of carcinogenic heterocyclic amines in the Chinese diet: results from a 24-h dietary recall study in Singapore.

OBJECTIVE: Heterocyclic amines (HCAs) from high-temperature cooking of meat have been linked to increased cancer incidence in Western populations, but data on the sources of HCAs in Asian diets are scarce. Our aim was to identify potential sources of HCAs in the Chinese diet, and to provide the basis for efforts to quantify dietary exposure to these compounds. DESIGN AND SETTING: We conducted 24-h dietary recall interviews among 986 Chinese men and women in Singapore, who were a randomly selected subpopulation of participants from the Singapore Chinese Health Study, a population-based cohort. Details of all foods and beverages consumed by each subject in the past 24 h were recorded, and information on meat type, cooking method and portion size were abstracted from all meat-containing dishes, and gram weight equivalents computed. RESULTS: The mean meat intake per person was 103.0 g/day (standard deviation 74.2), of which 97.2% was fresh meat. Fish (38.0%), pork (30.6%), and poultry (21.0%) accounted for 89.6% of meat consumed. Patterns of meat consumption and cooking methods differed markedly from Western populations. Documented high-temperature cooking methods, combined with stir-frying, accounted for 44.3% of fish, 35.1% of pork and 25.6% of poultry consumed. Specifically, potentially significant sources of HCAs were pan-fried fish and barbecued pork. CONCLUSIONS: Our results identify the potential sources of HCA in the Chinese diet, highlight aspects which are relevant to HCA formation and intake, and call for novel approaches to estimating individual exposure to dietary HCAs in this and similar populations.

Isoflavonoid levels in spot urine are associated with frequency of dietary soy intake in a population-based sample of middle-aged and older Chinese in Singapore.

Soy products contain high amounts of isoflavonoids, which have been shown to exhibit possible cancer-protective properties. Chinese populations in Asia, in particular, have a high level of soy intake and a relatively low risk of hormone-dependent cancers. In this study, we assessed the distributions of dietary soy isoflavonoids (daidzein, genistein, and glycitein) and urinary soy isoflavonoids and their metabolites (daidzein, genistein, glycitein, equol, and O-desmethylangolensin) among 147 Singapore Chinese (76 men and 71 women) ages 45-74 years, who are participants of the Singapore Cohort Study on diet and cancer. Urinary values were measured from spot samples collected 10-20 months following recruitment, when usual dietary habits were assessed by a structured food frequency/portion size questionnaire administered in person. Dietary levels of daidzein and genistein were comparable within individuals and about seven times higher than the level of dietary glycitein. All three dietary isoflavonoids showed an approximately 3.5-fold difference between the 25th and 75th percentile values. Similarly, daidzein was the most abundant and glycitein the least abundant of the five isoflavonoid compounds in urine. There was a 4.9-fold difference between the 25th and 75th percentile values for the sum of the five urinary isoflavonoids. Among study subjects, there were statistically significant, dose-dependent associations between frequency of overall soy intake and levels of urinary daidzein (two-sided P = 0.03) and sum of urinary daidzein, genistein, and glycitein (two-sided P = 0.04). In contrast, there were no associations between frequency of overall soy intake and levels of the two daidzein metabolites (equol and O-desmethylangolensin) in urine (two-sided P = 0.85 and 0.34, respectively). We suggest that within the range of exposures experienced by Singapore Chinese, urinary level of daidzein or the sum of daidzein, genistein, and glycitein obtained from a spot sample can serve as a biomarker of current soy consumption in epidemiological studies of diet-disease associations.

Urinary total isothiocyanate (ITC) in a population-based sample of middle-aged and older Chinese in Singapore: relationship with dietary total ITC and glutathione S-transferase M1/T1/P1 genotypes.

Isothiocyanates (ITCs), degradation products of glucosinolates (which occur naturally in a variety of cruciferous vegetables), have been shown to exhibit chemopreventive activity. These compounds are metabolized in vivo to form the corresponding dithiocarbamates, which are the major urinary metabolites of ITCs, by a pathway involving the glutathione S-transferase (GST) class of enzymes. Using a newly developed assay that measures total ITC (primarily ITC conjugates) in urine, we examined the relationships between cruciferous vegetable intake (obtained from a food frequency/portion size questionnaire administered in person); dietary total ITC level; GSTM1, GSTT1, and GSTP1 genotypes; and levels of total ITC in spot urine samples collected from 246 Singapore Chinese (111 men and 135 women), ages 45-74 years, who are participants of the Singapore Cohort Study on diet and cancer. Consumption level of cruciferous vegetables was high in study subjects (mean consumption = 345 times per year, mean daily intake = 40.6 g), which was >3 times the comparable level of intake in the United States. Mean daily intake of total ITC among study subjects was 9.1 micromol, and there was a 2.5-fold difference between the 25th and 75th percentile values. Seventy-three % of study subjects tested positive for ITC in urine, and there was a 4-fold difference between the 25th and 75th percentile values among the positive subjects. There was a highly significant positive association between dietary intake and urinary excretion levels of total ITC (two-sided P = 0.0003) that was stronger than the association between overall cruciferous vegetable intake and urinary ITC level, which also was statistically significant (P = 0.0004). There was no difference in urinary ITC levels between GSTM1-null and GSTM1-positive study subjects (P = 0.61) or between subjects with differing GSTP1 genotypes (P = 0.77), but urinary excretion of ITC was significantly higher among GSTT1-positive subjects, relative to GSTT1-null subjects (P = 0.006). The strength of the association between GSTT1 genotype and urinary total ITC level was highly dependent on the level of cruciferous vegetable consumption (or dietary ITC level) in study subjects. Among subjects in the lowest tertile of cruciferous vegetable intake, there was little evidence of an association between GSTT1 genotype and urinary total ITC level (P = 0.67). In contrast, there was a strong and statistically significant association between GSTT1 genotype and urinary total ITC among subjects in the highest tertile of cruciferous vegetable intake (P = 0.02), whereas those in the middle tertile of cruciferous vegetable consumption exhibited an association of intermediate strength (P = 0.04). These results suggest the presence of GSTT1 inducers in cruciferous vegetables.

Fumes from meat cooking and lung cancer risk in Chinese women.

Chinese women are recognized to have a high incidence of lung cancer despite a low smoking prevalence. Several studies have implicated domestic exposure to cooking fumes as a possible risk factor, although the exact carcinogens have yet to be identified. Heterocyclic amines are known carcinogens, which have been identified in cooked meat, and also in fumes generated during frying or grilling of meats. We conducted a case-control study of 303 Chinese women with pathologically confirmed, primary carcinomas of the lung and 765 controls to examine the association between exposure to meat cooking and lung cancer risk. Data on demographic background, smoking status, and domestic cooking exposure, including stir-frying of meat, were obtained by in-person interview while in hospital. The response rates among eligible cases and controls were 95.0 and 96.9%, respectively. The proportion of smokers (current or ex-smokers) among cases and controls was 41.7 and 13.1%, respectively. Adenocarcinomas comprised 31.5% of cancers among smokers and 71.6% among nonsmokers. When cases were compared with controls, the odds ratio (OR) for lung cancer (all subtypes) among ex-smokers was 4.3 [95% confidence interval (CI) 2.7-6.8] and that among current smokers was 5.0 (95% CI, 3.4-7.3). Among smokers, women who reported that they stir-fried daily in the past had a significantly increased risk of lung cancer (adjusted OR, 2.0; 95% CI, 1.0-3.8) and among these women, risk was enhanced for those who stir-fried meat daily (OR, 2.7; 95% CI, 1.3-5.5). Women who stir-fried daily but cooked meat less often than daily did not show an elevated risk (OR, 1.0. 95% CI, 0.5-2.4). Risk was further increased among women stir-frying meat daily who reported that their kitchen was filled with oily fumes during cooking (OR, 3.7; 95% CI, 1.8-7.5). These cooking practices on their own did not increase risk among nonsmokers in our study population. Our results suggest that inhalation of carcinogens, such as heterocyclic amines generated during frying of meat, may increase the risk of lung cancer among smokers. Further studies in different settings are warranted to examine this possibility, which may also help to explain the higher risk observed among women smokers compared with men.

Dietary isothiocyanates, glutathione S-transferase -M1, -T1 polymorphisms and lung cancer risk among Chinese women in Singapore.

Chinese populations consume a diet relatively high in isothiocyanates (ITCs), a derivative of cruciferous vegetables known to have cancer-protective effects. This class of compounds is metabolized by the glutathione S-transferase family of enzymes, which are also involved in the detoxification of tobacco-related carcinogens such as polycyclic aromatic hydrocarbons and alkyl halides. We evaluated the association between dietary isothiocyanate intake, GSTM1 and GSTT1 polymorphisms, and lung cancer risk in 420 Chinese women: 233 histologically confirmed lung cancer patients and 187 hospital controls. Among these, 58.8% of cases and 90.3% of controls were lifetime nonsmokers. An allele-specific PCR method was used to detect the presence or absence of the GSTM1 and GSTT1 genes in DNA isolated from peripheral blood. Higher weekly intake of ITCs (above the control median value of 53.0 micromol) reduced the risk of lung cancer to a greater extent in smokers [adjusted odds ratio (OR), 0.31; 95% confidence interval (CI), 0.10-0.98] than nonsmokers (OR, 0.70; 95% CI, 0.45-1.11). The inverse association was stronger among subjects with homozygous deletion of GSTM1 and/or GSTT1. Among nonsmokers with GSTM1-null genotype, higher intake of ITCs significantly reduced the risk of lung cancer (OR, 0.54; 95% CI, 0.30-0.95), an effect not seen among those with detectable GSTM1 (OR, 1.07; 95% CI, 0.50-2.29). Our results, in a Chinese female population, are consistent with the hypothesis that ITC is inversely related to the risk of lung cancer, and we show that among nonsmokers this effect may be primarily confined to GST-null individuals. Conjugation and elimination of ITCs is enhanced in GST-non-null relative to -null individuals, such that the GST metabolic genotype modifies the protective effect of ITCs on lung cancer development.

Patterns of consultation and treatment for heartburn: findings from a Singaporean community survey.

BACKGROUND: The prevalence of reflux-type symptoms among community individuals in Singapore is low. AIM: To describe the healthcare-seeking behaviour of those subjects with heartburn. METHODS: A cross-sectional survey, using a reliable and valid questionnaire, was carried out on a race-stratified random sample of residents, aged 21-95 years, in a Singaporean town; 93% responded (n = 696). RESULTS: The ethnic-adjusted prevalence of heartburn for the past 1-year was 4.6%. Sixteen (30%) of the 53 heartburn sufferers had sought consultation for their symptoms. They were more likely to have severe heartburn (P<0.001), and to have complained of nocturnal awakening due to heartburn (P<0.05) than those who did not present to medical attention. Ethnic origin did not influence the consultation pattern. Only 18 (34%) of the 53 heartburn sufferers received pharmacological therapy for their symptoms. The most commonly used medication was antacid. Medication use was associated with symptom severity (P<0.05), but not ethnicity. CONCLUSIONS: Heartburn is uncommon in the general population of Singapore. Few heartburn sufferers seek medical attention, and most do not receive medications for symptomatic control. The decision to seek medical advice and/or to medicate was generally linked to symptom severity, but not to ethnicity.

Survival among Chinese women with lung cancer in Singapore: a comparison by stage, histology and smoking status.

Lung cancer generally carries a poor prognosis and the determinants of survival have been of interest. However, survival estimates in Asian populations are scarce. This study describes survival rates and their determinants in Singapore Chinese women, a primarily non-smoking population. Three hundred and twenty-six Chinese women, diagnosed with primary lung carcinoma in three major hospitals in Singapore between April 1996 and December 1998, were followed up till 31 December 2000. The Kaplan-Meier method was used for survival analysis. Two hundred and eighty (85.7%) died from the disease during follow-up. The median survival time was 0.7 years and the three-year survival was 15.8%. These survival rates are similar to those of Western populations, and they provide a basis for examining trends over time. Age at diagnosis was an independent prognostic factor [adjusted hazard ratio (relative risk) 1.4, 95% confidence intervals (CI) 1.1-1.9 for women above 65 years relative to younger women]. Most (70.5%) tumours were stage III/IV at diagnosis. Three-year survival ranged from 72% among patients with stage I tumours to 7% for stage IV tumours. Overall, there was no survival difference among different histological types in all stages combined. When limited to stages I and II cancers, adenocarcinomas were associated with a better outcome relative to other histological subtypes combined (adjusted relative risk 0.4, 95% CI 0.1-1.0). Smoking was an independent risk factor (adjusted relative risk 1.3, 95% CI 1.0-1.8). Nevertheless, non-smokers comprised 57.4% of this series, highlighting the importance of increased awareness among health professionals and the public that lung cancer is not only a disease of smokers. The high proportion of late-stage tumours in this study and the impact of disease stage on outcome underline the importance of early detection in improving survival of lung cancer.

Breast cancer in Singapore: trends in incidence 1968-1992.

BACKGROUND: Breast cancer is the most commonly occurring cancer among women in Singapore, a country which has experienced significant changes in lifestyle over the past three decades. The increase in incidence of the disease is a matter of some concern. METHODS: Data from the population-based Singapore Cancer Registry for 1968-1992 were used to determine time trends, inter-ethnic differences and the contributions of age, period and cohort effects to the incidence of the disease. RESULTS: Our results revealed an average annual increase of 3.6% over the 25-year period for all women, form 20.2 per 100,000 women in the period 1968-1972 to 38.8 per 100,000 in 1988-1992. There was a statistically significant difference between the three major ethnic groups, the rate of increase being highest in Malays (4.4%) and lowest in Indians (1.4%). The overall increase was attributable to a strong cohort effect that remained significant when adjusted for time period for Chinese women and for all ethnic groups combined. The risk was observed to increase in successive birth cohorts from the 1890s to 1960s. CONCLUSIONS: Our results suggest that breast cancer incidence rates are likely to continue to increase more sharply in the future as women born after the mid-20th century reach the high-risk age groups. They also suggest the pattern by which important aetiological factors for the disease in our population have exerted their effects, and provide support for the role of demographic and lifestyle changes as possible risk factors.

Lung cancer among Chinese females in Singapore 1968-1992: time trends, dialect group differences and implications for aetiology.

BACKGROUND: Chinese females are distinguished internationally as having relatively high lung cancer incidence rates despite a low prevalence of cigarette smoking. In Singapore, this population comprises several dialect groups which have origins in different regions in China, each with its own traditional cultural practices. METHODS: An analysis of 4029 incident cases of the disease notified to the Singapore Cancer Registry for 1968-1992 was undertaken to provide some insight into important aetiologic factors among these women. RESULTS: The age-standardized incidence rate of lung cancer rose from 17.3 per 100,000 woman-years in 1968-1972 to 23.0 in 1978-1982 before falling off in more recent years. Age-period-cohort analysis indicated significant period and birth cohort effects, with the risk being highest for women born around 1908. Between the major dialect groups, Cantonese women had a significantly high rate compared with Hokkiens (relative risk [RR] = 2.6, 95% CI: 2.4-2.8). Histologically, there appears to be an increase in the proportion of adenocarcinomas diagnosed over this period (25.8% in 1968-1972 to 51.3% in 1988-1992). CONCLUSION: Our results suggest that traditional practices which have decreased over the years, and are more prominent among Southern Chinese, may play a part in the aetiology of lung cancer locally.

Attitudes as barriers in breast screening: a prospective study among Singapore women.

Health care systems do not exist in isolation, but rather, as part of the larger social and cultural mosaic. In particular, perceived attitudes are major obstacles in health promotion exercises. This problem is especially true for non-white populations where little is known about the prevailing social and cultural perceptions towards western biomedical prescriptions. To further our understanding of Asian women's acceptance of mammograms, three attitudinal indexes are conceptualised, constructed and validated. Data from a prospective survey showed the significance of fatalistic attitudes, perceived barriers and perceived efficacy of early detection in predicting women's acceptance of a free mammogram at the National Breast Screening Project. In addition, findings reinforced the importance of social support from the family in the promotion of breast screening among Asian women.

A cross-sectional survey of physical activity among middle aged women in Singapore.

OBJECTIVES: To assess the extent to which middle-aged women in Singapore engage in physical activity of a level which would result in long-term health benefits, and to determine the factors associated with this. METHODS: We conducted a cross-sectional survey of women aged between 35 and 60 years residing in Marine Terrace. A standardised questionnaire incorporating a modified Seven-Day Recall Questionnaire was used to record the level and type of physical activity engaged in over the past week. Demographic information and factors promoting or discouraging sports and exercise were also elicited. The total energy expenditure for household, occupational and sports activities of moderate intensity and above was calculated using metabolic equivalents (METs) in kcal/kg/week. RESULTS: Of the 341 respondents, 50.7% reported engaging in at least moderate activity for 30 minutes or more every day during the past week, thus fulfilling the WHO recommendations on physical activity. Housework contributed significantly to the energy expenditure on these activities among our target population. After adjusting for age, body mass index and educational level, we found that housewives without domestic help were most likely to fulfill the WHO recommendations. Housewives or working women with domestic help were the two groups at highest risk of low physical activity. A lack of time was the reason most commonly cited for not engaging in sports or exercise. CONCLUSION: Studies assessing physical activity in relation to disease risk among women should include domestic work in addition to the traditional leisure-time activities. There is a scope for further efforts to improve the level of activity in this population, which could be facilitated by the support of health professionals, employers and family members.

Prevalence and determinants of cervical cancer screening: a community-based study in Singapore.

A cross-sectional survey of 568 married women aged 21-65 years in the Pasir Panjang Constituency was conducted to determine the prevalence of cervical cancer screening in the community and the factors affecting acceptance of this screening test. Results show that 309 (54.4%) of the respondents had ever had a Pap smear. The women who reported having had a smear were more likely to be below 45 years of age (prevalence ratio 1.47, 95% confidence interval 1.15 to 1.88), Chinese and of a higher socioeconomic status (1.68, 1.33 to 2.12). They were also more likely to have married at a later age (1.68, 1.21 to 2.31) than women who had not had a smear. Age and socioeconomic status remained independent predictors on multivariate analysis. The findings suggest that an important task of public health practitioners is to increase the uptake of screening among older and socially disadvantaged women who are known to be at the highest risk of cervical cancer. In addition, strategies to encourage younger women to continue regular attendance at screening clinics beyond their childbearing years will be important for the future.

Cervical cancer: trends in incidence and mortality in Singapore 1968 to 1987.

Analysis of data collected by the population-based Singapore Cancer Registry reveals that the age-standardised incidence of cervical cancer has decreased from 18.2 per 100,000 females in 1968-72 to 16.2 per 100,000 in 1983-87, and its ranking among the most common female cancers has fallen from second to fourth place behind cancers of the breast, colon/rectum and lung. Mortality from the disease has also shown a corresponding fall from 7.3 per 100,000 to 5.5 per 100,000 women over the same period. Cervical cancer incidence rates are in general highest among Indian women, intermediate in Chinese and lowest in Malays. Age-specific incidence curves over time show a marked fall in rates in women over 50 years of age, whereas younger women (35-44 years old) show a small increase. A similar increase in rates has been observed in various other countries. Internationally, Singapore's incidence rate falls between the highs of South America and parts of Asia, and the lower rates of North America and Europe. The decrease in rates is comparable with the overall global trend, but falls short of that achieved by countries with systematic cytological screening programmes.

Awareness and acceptance of hepatitis B vaccination in Clementi, Singapore.

Hepatitis B Virus infection, a public health problem in Singapore, can be effectively controlled by vaccination. This paper reports on a study conducted in 1988/89 to ascertain the awareness and uptake rate of Hepatitis B vaccination. A list of children born between November 1986 and May 1987 in the catchmen zone of the Clementi Maternal and Child Health (MCH) Clinic was obtained. Out of a total of 257 children, 226 (87.9%) responded to our study in May 1988 which was part of a larger community health survey carried out by a group of medical students. The vaccination uptake rate was 23%. The awareness of the parents on Hepatitis B virus infection and vaccination was assessed using a standardised questionnaire. About two-thirds were aware of the main modes of Hepatitis B transmission, 46.5% were aware of the long-term consequences of Hepatitis B infection and 6.6% thought that the vaccine was not safe from serious side effects. A follow-up survey of the respondents was carried out in August 1989. The Hepatitis B vaccination uptake had increased to 48.3%. The immunisation status showed a correlation with the ethnic group, father's occupation and awareness score of respondents. The more than two-fold increase in uptake rate can be attributed to a reduction in the cost of Hepatitis B vaccination and a vigorous nation-wide education programme during the preceding year.

Trends in cancer incidence among Singapore Malays: a low-risk population.

INTRODUCTION: Inspection of trends in cancer incidence in ethnically or geographically diverse populations is important for the understanding of cancer patterns and also to provide clues for aetiologic studies. There is little information on cancer incidence among Malays, a low-risk population. The population-based cancer registration system in Singapore offers the opportunity in this regard. MATERIALS AND METHODS: A review of all newly diagnosed cancer cases among Singapore Malay residents in the period 1968 to 1997 was conducted to determine the time trends using data from Singapore Cancer Registry. Age-standardised incidence rates and average annual percentage change, using Poisson regression, were calculated. RESULTS: During the 30-year study period, a total of 9101 incident cases of cancer were diagnosed among Malays in Singapore. The 3 most common sites of cancer were lung, liver and colorectum in males; and breast, colorectum and ovary in females in the period 1983 to 1997. Leukaemia was among the top 10 cancer sites in both sexes. Malays generally experienced lower cancer incidence rates compared to Chinese, but rates have been increasing at 1.5% to 2% annually. Statistically significant increases in incidence were observed for most of the cancer sites. The incidence of nasopharyngeal carcinoma increased, while there were no significant changes in the general population. CONCLUSION: The relatively lower cancer risk among Singapore Malays might be attributed to genetic factors or closer adherence to a more traditional lifestyle. This study provides a baseline for comparisons with other populations with diverse cancer risk patterns in order to obtain a better understanding of possible aetiologic factors.

Survival of colorectal cancer patients in Singapore by anatomic subsite: a population-based study.

INTRODUCTION: Studies of the prognostic value of anatomic subsite in colorectal cancer survival have yielded conflicting results. Two explanations for possible differences in survival patterns between proximal and distal lesions in the colorectum are biological difference between subsites and the presence of more early-stage lesions in distal than in proximal large bowel. MATERIALS AND METHODS: A total of 435 cases with proximal lesions and an equal number with distal lesions diagnosed between 1990 and 1992 were randomly selected from the Singapore Cancer Registry. Information on vital status at 31 December 1996 were obtained by computerised matching with data from the National Registry of Births and Deaths. RESULTS: Persons with proximal cancers in our study population did not present at a later stage than persons with distal cancer, local lesions (Dukes' Stage A + B) being 45.5% and 45.1%, respectively. Our analysis showed no significant differences in survival between subsites on a stage-for-stage basis. The 5-year survival rates were 42% and 44% for proximal and distal lesions, respectively (median survival times 3.98 and 4.27 years). Stage at diagnosis was the strongest predictor of survival. Among proximal lesions, 5-year survival rates were 57%, 36% and 12% for local, regional and metastatic lesions, respectively. The corresponding figures for the distal group were 65%, 37% and 10%. Age at diagnosis had a significant influence on survival. CONCLUSIONS: Our results, based on population-based figures on survival of colorectal cancer patients where the impact of screening has not been large, do not support an independent influence of anatomic subsite in predicting survival of colorectal cancer.

A randomized trial of the use of print material and personal contact to improve mammography uptake among screening non-attenders in Singapore.

The Singapore Breast Screening Project was a nationwide study inviting a random sample of women between the ages of 50 and 64 years for mammography at one of two hospital-based screening centres over two years. The current study was undertaken to determine if (1) mailed health educational material alone, or (2) the same material delivered during a home visit made to the subject and her family would increase the uptake among Singapore women who had not responded to two previous invitations for mammographic screening as part of the Project. This randomized trial employed a standard second reminder letter (R), the same letter packaged with health education material designed for the project (RP) and the addition of a home visit to make contact with the woman and her family (RV). The outcome measure of interest was the proportion of women in each group subsequently attending for screening. The study population comprised 1500 non-attenders whose names appeared consecutively in the database of the larger screening centre in this Project. These were randomized into three groups of 500 each. In total, they broadly resembled the national population in ethnic composition (72.3% Chinese, 17.8% Malays, 9.0% Indians and 0.8% Others). By the end of the project, 7.0% of women in group R and 7.6% in group RP responded to the invitation. In group RV, 428 homes were visited at least once and contact was made with the subject and her family member in 306 (71.5%) cases. Subsequently, 13.3% of the women visited attended for screening. The rate ratio for attendance in group RP compared with group R was 1.09 (95% CI 0.70 to 1.70) and for group RV compared with R, 1.90 (1.27 to 2.84). When analyzed by groups originally assigned to, women in group RV remained significantly more likely to attend than those in groups R or RP. The marginal cost of a home visit, based on this study, was $25.04 per additional woman screened. Our results suggest that the response to a second reminder is generally low and that additional print material does not improve screening attendance in this group of initial non-attenders. Personal contact with the family through a home visit appears to increase uptake, and may be helpful particularly among women who have less frequent contact with the health care system.