Levels of Cardiovascular Disease Risk Factors in Singapore Following a National Intervention Programme. (Theme Paper)

Article excerpt

Voir page 914 le resume en francais. En la pagina 914 figura un resumen en espanol.

Introduction

The island of Singapore has undergone rapid socioeconomic development since independence in 1965. For example, the per capita gross national product, adjusted to 1998 prices, rose from S$ 1618 in 1965 to S$ 38 170 in 1998 (US$ 1.0 = S$ 1.70). In 1998, the infant mortality rate was 4.1 per 1000 live births and life expectancy at birth was 79 years for females and 75 years for males. Other 1998 indicators include an adult literacy rate of 93%, and 13 doctors per 10000 population (1). The total population of Singapore in 1998 was 3.87 million and it had the second highest population density in the world (after Hong Kong Special Administrative Region of China) at 5965 people per [km.sup.2]. The resident population consisted of 77% Chinese, 14% Malay, 7.6% Indian, and 1.4% other ethnic groups. The main causes of mortality in Singapore mirrored those of developed countries, with cancer, ischaemic heart disease, and cerebrovascular disease responsible for 57% of all deaths in 1998 (2). These three diseases have been the main causes of death in Singapore since the 1970s.

In 1991, a national committee was appointed to review the national health plan for the 1990s, and one of the key recommendations emphasized health promotion and disease prevention (3). This was followed by the National Healthy Lifestyle Programme in 1992, which adopted a multisectoral approach involving government ministries and organizations, health professionals, employers, unions, and community organizations. These sectors worked together to provide information, skills training, and the social and physical environment necessary to encourage healthy living by Singaporeans. The programme included extensive use of the mass media to promote healthy lifestyles, legislative measures to discourage smoking, and widespread school, workplace, and community health promotion programmes. The programmes emphasized healthy diets, regular physical exercise, and measures to discourage smoking.

In 1992, the Ministry of Health also conducted the first National Health Survey (NHS), a population-based cross-sectional survey to measure the prevalence of diabetes mellitus, hypertension, obesity, smoking, physical inactivity, and hypercholesterolaemia -- all cardiovascular disease risk factors. Findings from the survey provided baseline data for subsequent evaluation of the effectiveness of the National Healthy Lifestyle Programme. In 1998, six years after the launch of the National Healthy Lifestyle Programme, a second NHS was conducted to determine whether the risk factors in the population had changed.

Methods

The NHS was a cross-sectional survey conducted between September and November, 1998. The reference population was 2.16 million Chinese, Malay, and Indian Singapore residents aged 18-69 years. Six centres around the island of Singapore were selected as field sites for the survey. Details of the survey methodology have been described elsewhere (4).

Determination of sample size

We calculated that a sample size of 5000 respondents would be required to detect a 10-15% change from baseline for most of the diseases and risk factors with 80% power. The prevalence of diabetes mellitus, hypertension, and other cardiovascular risk factors (obesity, smoking, and physical inactivity) measured in the 1992 NHS was used as baseline levels. To account for potential non-response during the survey, we estimated that at least 10000 households would need to be approached to obtain the target sample size.

Sample selection

The sample selection was divided into two phases. In phase I, a sample of 11 200 household addresses was selected from the National Database on Dwellings. The sample selection was based on a modified two-stage stratified design. For the first stage, sampling divisions close to the six selected survey centres were chosen and households within each division were stratified by house type (a proxy for socioeconomic status) and systematically selected in the second stage. …