Firstly, it is important to point out that almost all recently published cohort research (described in this Chapter) related to obesity in Singapore were based on selective pooling of various cross-sectional national surveys, in which respective participants, mostly adults, were contacted for subsequent follow-up health screening or monitoring of particular chronic conditions. Briefly, these surveys included a random sample of individuals from the Singapore population, with disproportionate sampling stratified by ethnicity to increase the number in the minority ethnic groups (Malays and Indians). Although their clinical objectives were different, the surveys had common data collection instruments and comparable clinical assessment
protocols, including anthropometric measurements, such as weight and height, to allow merging of datasets. Table 32 presents a summary of selected longitudinal studies relevant to the study of obesity in Singapore.
Table 32 Summary of selected longitudinal cohorts relevant to the study of obesity in Singapore
Cohort name (year established)
Size Data sources Primary research objective
Singapore Cardiovascular Cohort Study (2000)
5,920 Thyroid and Health Survey 1982-1984, National Health Survey 1992 and National University of
Singapore Heart Study 1993-1995
To study incidence of ischemic heart disease and stroke among Chinese, Malays and Asian Indians
Singapore
Prospective Study Program (2007)
10,445 Thyroid and Heart Study 1982–
1984, National Health Survey 1992, National University of Singapore Heart Study 1993–1995, and National Health Survey 1998
To examine the pathogenesis of cardiovascular and metabolic
9,217 NUS Diabetes Cohort Study, Singapore Prospective Study Program, and Singapore Cardiovascular Cohort Study 2
To investigate the genetic and lifestyle factors affecting the
Individuals (with Type 2 Diabetes) recruited from National Healthcare Group Polyclinics, National University Hospital Singapore and the Tan Tock Seng Hospital
To identify genetic and
1,979 Healthy children from grades 1-3 (age 7 to 9) who were recruited from three schools in Singapore (located in the Eastern, Western and Northern regions)
To determine the risk factors of incident myopia in a
1,163 Healthy pregnant women were recruited in their first trimester and subsequently their offspring would be part of the study
To evaluate the role of developmental factors in the early pathways to metabolic compromise, namely obesity and Type 2 Diabetes Mellitus.
4.1.2.2 Singapore Cardiovascular Cohort Study
The Singapore Cardiovascular Cohort Study (SCS) was the first prospective cohort study in Singapore to describe the incidence of ischemic heart disease (IHD) and stroke among
Chinese, Malays and Asian Indians in 2000. A total of 5,920 people, of which 2,920 were male, comprised the cohort, composed of participants from three previous cross-sectional surveys: the Thyroid and Health Survey 1982-1984, the National Health Survey 1992 and the National
University of Singapore Heart Study 1993-1995. Morbidity and mortality from IHD and stroke were ascertained by record linkage using a unique identification number with the death registry, Singapore Myocardial Infarct Registry and in-patient discharge databases (155).
Subsequently, the cohort was followed up over 10 years for a number of other outcome measures, such as for relationships of established coronary risk factors with incident coronary heart disease (156), the effect of pre-hypertension (157), hypertension alone, and in combination with other CVD risk factors on all-cause and CVD mortality (158).
4.1.2.3 Singapore Prospective Study Program
The Singapore Prospective Study Program (SP2) was a cross-sectional study of adult Singaporean Chinese, Malay and Asian-Indian samples, aged between 24 to 95 years. The methodology of constructing the study sample has been described in detail elsewhere (159).
Briefly, 10,445 subjects from 4 population-based, cross-sectional surveys conducted in
Singapore (1982–1998) were invited to participate in a repeat examination from 2004 to 2007.
The four studies include the Thyroid and Heart Study 1982–1984, the National Health Survey 1992, the National University of Singapore Heart Study 1993–1995, and the National Health Survey 1998. A total of 7,742 (74.1% response rate) subjects completed the investigator-administered questionnaire at their homes; 5,157 of them (66.6% of those who completed the questionnaire or 49.4% of all eligible subjects) also attended an in-person health examination.
The availability of a large number of healthy participants has offered the opportunity for researchers to examine the relation between fasting plasma glucose and the prevalence of chronic
kidney disease and peripheral neuropathy in a large population spanning the full range of glucose tolerance (159). Participants from the SP2 have also been followed up to explore and compare health-related quality of life levels in the three main ethnic groups in Singapore: Chinese, Malay, Indian (159).
4.1.2.4 Singapore Consortium of Cohort Studies
The Singapore Consortium of Cohort Studies (SCCS) was a research initiative funded by the Biomedical Research Council (BMRC). This large prospective study aimed to investigate the genetic and lifestyle factors affecting the risk of developing various chronic diseases such as diabetes, cancer, and heart disease. The SCCS is composed of two major arms, a diabetic cohort (DC), and a multi-ethnic cohort (MEC). The DC will build on the existing NUS Diabetes Cohort Study of 3,900 diabetic patients who were previously recruited. The MEC is a cohort of normal people aged 21 to 75 who will be followed up in 3-5 year intervals for the development of a wide range of diseases. The MEC builds on two existing cohort studies, the Singapore Prospective Study Program (SP2), and the Singapore Cardiovascular Cohort Study 2 (SCCS2). At the end of July 2007, there were a total of 5,214 subjects in the MEC and 4,003 patients in the DC (160).
Essentially, the SCCS was a national effort to pool selected cohort studies and build on these to develop a large multi-ethnic population-based cohort study to facilitate research into the complex gene-environment interactions in diseases such as diabetes, cardiovascular diseases and cancers. It also served to provide a large variety of healthy controls, which can be matched with regards to age or ethnicity for current on-going case-control studies (160).
4.1.2.5 Singapore Diabetes Cohort
The Singapore Diabetes Cohort (SDCS) included Singaporean Chinese, Malay, and Asian-Indian adults with type 2 diabetes and had been published previously (161). These individuals were recruited from National Healthcare Group Polyclinics, National University Hospital Singapore and the Tan Tock Seng Hospital. The study had a participation response rate of 90% with over 5,000 patients recruited.
4.1.2.6 Singapore Cohort study Of the Risk factors for Myopia
The Singapore Cohort study Of the Risk factors for Myopia (SCORM) (162) is a prospective study consisting of 1,979 children from grades 1-3 (age 7 to 9) who were recruited from three schools in Singapore (located in the Eastern, Western and Northern regions). Children with serious medical conditions such as heart disorders and leukaemia were excluded from the study (n=94). BMI measures were taken at each annual follow up visits.
4.1.2.7 Growing Up in Singapore Towards healthy Outcomes
Growing Up in Singapore Towards Healthy Outcomes (GUSTO) is Singapore's largest and most comprehensive birth cohort study to date (163). With recruitment commencing in 2009, it is a currently on-going cohort study of pregnant women and their offspring, with recruitment beginning in the first trimester. The last GUSTO baby was born in May 2011. Mothers have been followed throughout pregnancy and their offspring will be examined until the child reaches 3 years of age. It is currently planned to continue follow-up through childhood and into adulthood.
The primary objective of the GUSTO birth cohort study is to evaluate the role of
developmental factors in the early pathways to metabolic compromise, namely obesity and Type 2 Diabetes Mellitus. Recruitment for the study was completed in September 2010 with 1,163 pregnant women recruited into the main GUSTO cohort (current drop-out rate = 12.1%). All of the women have delivered but data collection and analyses are still on-going. Amongst the participants recruited, 56% were Chinese, 26% Malay and 18% Indian. Of the babies delivered, at least 945 have reached 3 months of age by end-May 2011 (164).
The GUSTO study adopted a novel methodology to examine (in relation to clinical outcomes) the epigenetic effects of maternal diet, in addition to epigenetic markers at birth as a function of foetal growth and subsequently over development and its effect on allergy and other domains such as nutrition, prematurity, fertility, pregnancy, eye dental health and cognition. A unique feature of GUSTO is that the three distinct ethnic groups, Chinese, Malays and Indians, in the Singaporean population allows in-depth examination of the extent to which genomic
variation influences allergic phenotype (164).