Some of what we accept as "common knowledge" today, for example the strong link between high blood cholesterol and heart disease, the influence of smoking on lung cancer... this knowledge has been gained through long term health studies - cohort studies at that - in the US and UK, respectively. These cohorts have been assembled, traditionally, in Caucasian populations. However Asian populations differ from Caucasian ones, not only in geographical and lifestyle factors but also in terms of certain physical and genetic profiles.
Taking the case of breast cancer, where incidence rate has been about twice as high in Sweden as in Singapore, it is argued that postmenopausal breast cancer in these two countries differs in origin and tumour characteristics. The Swedish breast cancers could be more influenced by female sex hormones and thus have a different gene expression pattern. If this were the case, drug treatment for Singapore and Swedish breast cancer patients would be markedly different. It is possible that drugs which works well for most Swedish patients may not be as effective for the Singaporean patient.
In another example, many Asian populations, including Singaporeans, have higher proportion of body fat compared to Caucasians of the same age, gender and body mass index (BMI). In WHO's BMI Classification, normal BMI is 18.5 – 24.9 kg/m2. In March 2005 in Singapore, based on findings from local studies and the recommendations from the WHO Expert Consultation in Singapore, the healthy range was revised downwards to 18.5 – 22.9 kg/m2. This change was made in response to studies which showed that Asians have increased risk for cardiovascular diseases and diabetes mellitus at relatively low BMI levels.
Drugs do not always work the same way on people around the globe. Iressa (Gefitinib) started out as a promising lung cancer drug by AstraZeneca. It works by blocking cancer cell proliferation. After massive investment into this drug, faces fell when a large clinical trial could not prove that Iressa was more effective than a placebo. The United States Food and Drug Administration (FDA) began to review if Iressa should be removed from the market. However when the data was re-evaluated by ethnicity, it was found that Asians survived 9½ months longer, almost double the usual 5½ months. Iressa was effective in prolonging the survival of Asian lung cancer patients, even though it did not work as well on Caucasians. Scientists believe Asians respond well to this therapy because they are more likely to have certain genetic mutations in their cancer cells that Iressa is good at targeting.
These 3 examples merely scratch the surface of various medical mysteries waiting to be understood. An ethical and scientifically-sound long-term cohort study in Singapore will help us solve puzzles like these. I am committed to run this study in an ethical manner where top priority is given to safeguarding the privacy of our participants' data and samples. Our overarching aim is to discover ways to prevent common diseases and their complications, for the benefit of future generations.
Professor Chia Kee Seng Principal Investigator, Singapore Consortium of Cohort Studies
Director, Centre for Molecular Epidemiology
Yong Loo Lin School of Medicine National University of Singapore
