Levels of Cardiovascular Disease Risk Factors in Singapore Following a National Intervention Programme Jeffery Cutter,1 Bee Yian Tan,2 & Suok Kai Chew3
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Research Theme Paper Levels of cardiovascular disease risk factors in Singapore following a national intervention programme Jeffery Cutter,1 Bee Yian Tan,2 & Suok Kai Chew3 Objective To evaluate the impact of the National Healthy Lifestyle Programme, a noncommunicable disease intervention programme for major cardiovascular disease risk factors in Singapore, implemented in 1992. Methods The evaluation was carried out in 1998 by the Singapore National Health Survey (NHS). The reference population was 2.2 million multiracial Singapore residents, 18–69 years of age. A population-based survey sample (n = 4723) was selected by disproportionate stratified and systematic sampling. Anthropometric and blood pressure measurements were carried out on all subjects and blood samples were taken for biochemical analysis. Findings The 1998 results suggest that the National Healthy Lifestyle Programme significantly decreased regular smoking and increased regular exercise over 1992 levels and stabilized the prevalence of obesity and diabetes mellitus. However, the prevalence of high total blood cholesterol and hypertension increased. Ethnic differences in the prevalence of diabetes mellitus, hypertension, and smoking; and in lipid profile and exercise levels were also observed. Conclusion The intervention had mixed results after six years. Successful strategies have been continued and strengthened. Keywords Cardiovascular diseases/etiology/; Risk factors; Diabetes mellitus/epidemiology/ethnology; Hyper- tension/epidemiology/ethnology; Obesity/epidemiology/ethnology; Smoking/epidemiology/ethnology; Exercise; Ethnic groups; Life style; National health programs; Cross-sectional studies; Singapore (source: MeSH). Mots cle´s Cardiovasculaires, Maladies/e´tiologie; Facteur risque; Diabe`te/e´pide´miologie/ethnologie; Hyper- tension arte´rielle/e´ pide´miologie/ethnologie; Obe´site´/e´pide´miologie/ethnologie; Tabagisme/e´ pide´miologie/ethno- logie; Exercice physique; Groupes ethniques; Style vie; Programme national sante´ ; Etude section efficace; Singapour (source: INSERM). Palabras clave Enfermedades cardiovasculares/etiologı´a; Factores de riesgo; Diabetes mellitus/epidemiologı´a/ etnologı´a; Hipertensio´ n/epidemiologı´a/etnologı´a; Obesidad/epidemiologı´a/etnologı´a; Tabaquismo/epidemiologı´a/ etnologı´a; Ejercicio; Grupos e´tnicos; Estilo de vida; Programas nacionales de salud; Estudios transversales; Singapur (fuente: BIREME). Bulletin of the World Health Organization, 2001, 79: 908–915. Voir page 914 le re´sume´ en franc¸ais. En la pa´ gina 914 figura un resumen en espan˜ ol. Introduction For example, the per capita gross national product, adjusted to 1998 prices, rose from S$ 1618 in 1965 to The island of Singapore has undergone rapid socio- S$ 38 170 in 1998 (US$ 1.0 = S$ 1.70). In 1998, the economic development since independence in 1965. infant mortality rate was 4.1 per 1000 live births and life expectancy at birth was 79 years for females and 1 Deputy Director, Non-Communicable Diseases, Epidemiology & 75 years for males. Other 1998 indicators include an Disease Control Division (E&DC), Ministry of Health, College of adult literacy rate of 93% and 13 doctors per Medicine Building, 16 College Road, Singapore 169854 (email: [email protected]). Correspondence should be addressed 10 000 population (1). The total population of to this author. Singapore in 1998 was 3.87 million and it had the 2 Deputy Director, Biostatistics & Research, E&DC, Ministry of Health, second highest population density in the world (after Singapore. Hong Kong Special Administrative Region of China) 3 Director, E&DC, Ministry of Health, Singapore. at 5965 people per km2. The resident population Ref. No. 00-0677 consisted of 77% Chinese, 14% Malay, 7.6% Indian, 908 # World Health Organization 2001 Bulletin of the World Health Organization, 2001, 79 (10) Levels of cardiovascular disease risk factors in Singapore and 1.4% other ethnic groups. The main causes of Sample selection mortality in Singapore mirrored those of developed The sample selection was divided into two phases. In countries, with cancer, ischaemic heart disease, and phase I, a sample of 11 200 household addresses was cerebrovascular disease responsible for 57% of all selected from the National Database on Dwellings. deaths in 1998 (2). These three diseases have been the The sample selection was based on a modified two- main causes of death in Singapore since the 1970s. stage stratified design. For the first stage, sampling In 1991, a national committee was appointed to divisions close to the six selected survey centres were review the national health plan for the 1990s, and one chosen and households within each division were of the key recommendations emphasized health stratified by house type (a proxy for socioeconomic promotion and disease prevention (3). This was status) and systematically selected in the second followed by the National Healthy Lifestyle Pro- stage. The final sample of 11 200 addresses repre- gramme in 1992, which adopted a multisectoral sented the housetype distribution for the entire approach involving government ministries and Singapore housing population. This was followed up organizations, health professionals, employers, un- by house visits to enumerate all household members ions, and community organizations. These sectors aged 18–69 years. worked together to provide information, skills In phase II, a random sample of 7500 people training, and the social and physical environment was selected by disproportionate stratified and necessary to encourage healthy living by Singapor- systematic sampling of household members identi- eans. The programme included extensive use of the fied in phase I. The Malays and Indians were mass media to promote healthy lifestyles, legislative oversampled, to ensure that prevalence estimates measures to discourage smoking, and widespread for these minority groups were reliable. The ethnic school, workplace, and community health promotion composition of the sample was 64% Chinese, 21% programmes. The programmes emphasized healthy Malays, and 15% Indians. diets, regular physical exercise, and measures to discourage smoking. Survey protocol and procedures In 1992, the Ministry of Health also conducted The survey protocol closely followed that of the 1992 the first National Health Survey (NHS), a population- NHS to ensure comparability. The NHS protocol based cross-sectional survey to measure the pre- was based on the WHO-recommended model for valence of diabetes mellitus, hypertension, obesity, field surveys of diabetes and other noncommunic- smoking, physical inactivity, and hypercholestero- able diseases (5) and the WHO MONICA (Multi- laemia — all cardiovascular disease risk factors. national Monitoring of Trends and Determinants in Findings from the survey provided baseline data for Cardiovascular Disease) protocol for population subsequent evaluation of the effectiveness of the surveys (6). Subjects were instructed to fast over- National Healthy Lifestyle Programme. In 1998, six night for at least 10 hours before coming to the years after the launch of the National Healthy designated survey centre. A fasting blood sample was Lifestyle Programme, a second NHS was conducted collected and all subjects, except diabetics on to determine whether the risk factors in the medication, had an oral glucose tolerance test (7). population had changed. Other procedures included measuring blood pres- sure, height, weight, waist and hip circumference, and the administration of a structured questionnaire. Methods The 1985 WHO diagnostic classification criteria (7)wereusedtoclassifyglucosetolerance.Self-reported The NHS was a cross-sectional survey conducted diabetics on medication were also taken to be diabetics. between September and November, 1998. The Blood-pressure measurements followed procedures reference population was 2.16 million Chinese, prescribed in the WHO MONICA protocol (6). Malay, and Indian Singapore residents aged 18– Carefully trained observers took two measurements in 69 years. Six centres around the island of Singapore a quiet room after the subjects were rested. Hyper- were selected as field sites for the survey. Details of tension was defined according to WHO criteria: mean the survey methodology have been described else- systolic pressure 5140 mmHg; or diastolic pressure where (4). (phase V) 590 mmHg; or both; or self-reported current use of antihypertensive medication (8). Determination of sample size Smoking status and level of physical activity We calculated that a sample size of 5000 respondents were determined by questionnaires, which were would be required to detect a 10–15% change from administered by interviewers according to WHO baseline for most of the diseases and risk factors with guidelines (9) and the American College of Sports 80% power. The prevalence of diabetes mellitus, Medicine’s classification (10). Body mass index hypertension, and other cardiovascular risk factors (BMI) was measured as weight (kg)/height (m)2. (obesity, smoking, and physical inactivity) measured in The WHO classification of weight status and the 1992 NHS was used as baseline levels. To account abdominal fatness was used (11). The means of two for potential non-response during the survey, we readings of height and weight, as well as waist and hip estimated that at least 10 000 households would need circumferences, were used to calculate the body mass to be approached to obtain the target sample size. index and waist:hip ratio, respectively.