Diabetes in the South Asian Populations - Literature review Example

DIABETES IN SOUTH ASIAN POPULATIONS A REVIEW OF LITERATURE By Sarah Al Shaban Dr. E. Derbyshire Hollings Faculty Manchester Metropolitan University Word count 1411 Epidemiological research suggests that the prevalence of type 2 diabetes in South Asian populations is higher than that seen in other ethnic groups. (DECODA, 2003) Diabetes presents at a relatively earlier age and a lower BMI in this ethnic group.(2006) South Asian patients with type 2 diabetes in the UK have a higher cardiovascular risk and present with cardiovascular events at a significantly younger age than white Europeans.(2010) This review will provide an analysis of the available literature on the epidemiology of diabetes in South Asian populations. Three epidemiology papers relating to diabetes in South Asian populations, each employing a different study method will be discussed in the following review. Cross Sectional Study The higher prevalence of type 2 diabetes in South Asian populations in comparison to other ethnic groups was observed in a cross sectional study on the age and sex prevalence of diabetes mellitus among immigrants to Ontario, Canada. (2010) The study population consisting of 1,122,771 immigrants residing in Ontario, aged 20 years or older in 2005, was drawn from the Registered Persons Database(RPD), maintained by Citizenship and Immigration, Canada. The immigrants were identified by probabilistically linking the RPD with the Landed Immigrants Database which also contained information on education level, immigration category, age, sex and date of birth. The people who had been diagnosed with diabetes on or before 31st March 2005 were identified using the Ontario Diabetes Database; a validated administrative data registry updated using hospital and physician records. The postal codes of the subjects were linked to area level income from the 2006 Canadian Census, due to the unavailability of individual income data. Logistic regression was used to associate risk factors with the prevalence of diabetes. Risk factors included age, sex, level of education and world region of birth. After controlling for age, time since arrival, education level and immigration category, it was found that the prevalence of diabetes was significantly higher in immigrants from South Asia compared with those from Western and Eastern Europe and North America. Lower income levels were associated with a higher prevalence of diabetes and so was the time since arrival. (The prevalence of diabetes was significantly higher among those living in Canada for 15 years or more compared to those living in Canada for 5-9 years) A limitation of the study is the use of administrative data which only represents diagnosed diabetes. Thus it is possible that the prevalence of diabetes was underestimated in the study. It is also possible for the probability of diagnosis to differ with the country of origin and immigration status. A further limitation is the failure to distinguish between type 1 and type 2 diabetes. There are several hypotheses explaining the high prevalence of diabetes in South Asian populations. One of these is the thrifty phenotype hypothesis which links intrauterine growth retardation and catch up growth in early infancy to a higher risk in developing diabetes. (Stocker CJ et al., 2005) Conversely the thrifty genotype hypothesis refers to the metabolic adaptation to store adipose tissue as a survival advantage in circumstances of famine. (Neel, 1962) However several studies conducted to investigate its validity including a study by Southam et al. have revealed that there is no conclusive confirmation of the thrifty gene hypothesis. (2009) The role of lifestyle factors cannot be ignored when discussing the higher prevalence of diabetes in South Asians. The health survey of England has identified that Indians, Pakistanis and Bangladeshis are respectively 14%, 30% and 45% less likely to meet current guidelines for physical activity than the general population. (2004) Prospective Study It is important to understand whether there’s a significant difference in the mortality of patients with diabetes of South Asian origin compared with other ethnic groups. Forouhi et al. conducted a follow up of the Southall and Brent studies to analyse whether the measured risk factors could explain the higher coronary heart disease mortality in South Asians compared with Europeans. (2006) The study consisted of 3027 South Asian and European men from the Southall and Brent population based studies. Afro Caribbean men, men of other ethnic origin, men with cancer, renal failure, severe disabilities or sever psychiatric disturbances were excluded from the total available sample pooled in the Southall and Brent studies. Following an overnight fast the measurements taken included blood pressure, resting electrocardiogram and blood samples for glucose, insulin and lipids. Self administered questionnaires were used to gather information on smoking, physical activity, socio economic status and medical history. All participants were flagged for death notification from the Office for National Statistics. The analysis of data revealed that “In the South Asian group, diabetes increased the mortality risk nearly threefold compared with South Asians without diabetes at baseline, whereas in Europeans, the excess mortality associated with diabetes was only 1.5-fold.” This finding is different from the UK Prospective Diabetes Study, which concluded that South Asians with diabetes didn’t have a higher risk of developing myocardial infarction than whites. (UKPDS 32, 1998) However the UKPDS study and the Follow up of Southall and Brent studies were different in many respects including the former being conducted on a relatively young cohort with early onset diabetes and being in the form of a ‘clinical trial’ whereas the latter was conducted on ‘free living’ subjects. The limitations of the follow up of Southall and Brent study includes the lack of study data on the duration of diabetes in the subjects and the inherent limitations of measuring mortality based on the cause of death indicated in the death certificate(e.g. Errors in determining the cause of death). Interventional Randomised Control Study The high prevalence of diabetes among South Asians warrants specialist methods of intervention targeting specific cultural and social needs. Bellary et al. (2008) conducted a cluster randomized control trial to investigate the effectiveness of a culturally sensitive enhanced care package in UK general practice in improving cardiovascular risk factors in South Asian patients with type 2 diabetes. Twenty one general practices in Coventry and Birmingham, UK were randomized into two groups, one which received specialist methods of intervention and the other received standard intervention. The unit of randomization was a general practice. The study consisted of 1486 subjects, 868 in the intervention group that received enhanced practice nurse time, link worker and diabetes specialist nurse support and 618 in the control group that received standard care. Practice Nurses worked closely with primary care physicians to implement the protocol and to encourage appropriate prescribing and patient education in the clinic setting.. Link workers and community diabetes specialist nurses provided educational support while the latter provided additional clinical support including insulin initiation. Main outcome measures comprised changes in blood pressure, total cholesterol and glycaemic control (HbA1c) after 2 years. At baseline, groups were similar with respect to age, sex and cardiovascular risk factors. Comparing treatment groups, after adjustment for confounders, and clustering, differences in diastolic blood pressure (1.91mmHg, P=0.0001) and mean arterial pressure (1.36mmHg, P=0.0180) were significantly in favour of the intervention group. There were no significant differences between groups for total cholesterol or HbA1c. Economic analysis indicates the nurse-led intervention was not cost-effective. One limitation of the study was the use of last observation carried forward (LOCF) method for patients whose follow up data wasn’t available. However the analysis of completed data only, had produced very similar results. A further limitation was the inability to investigate the relative contributions of individual components of the intervention. Such an analysis may prove useful in future primary healthcare planning with regards to specialist interventions in the South Asian community. Another weakness observed is using general practice as the unit of randomization which may have led individual characteristics (e.g. Quality of service delivery of healthcare professionals) of the practices to affect the final outcome. Conclusions The articles summarized in this review demonstrate that the prevalence of type 2 diabetes is higher in South Asian populations and that it is associated with poorer cardiovascular outcomes compared to other populations. A specialist care package designed specifically for South Asian communities has shown to improve blood pressure but failed to result in significant glycaemic control. Further studies should focus on the factors affecting the morbidity and mortality of South Asians with diabetes and cost effective specialist care methods which could improve the health outcomes of this ethnic group. References Bellary S, O’Hare JP, Raymond NT , Gumber A, Mughal S, Szczepura A, Kumar S, Barnett AH. The United Kingdom Asian Diabetic Study.2008. Retrieved as pdf , 28/7/2010 from http://wrap.warwick.ac.uk/105/ Bellary S, OHare JP, Raymond NT, Mughal S, Hanif WM, Jones A, Kumar S, Barnett AH. (2010) CMRO 26:1873-1879 Creatore MI, Moineddin R, Booth G, Manuel DH, DesMeules M, McDermott S, Glazier RH. (2010) Age- and sex-related prevalence of diabetes mellitus among immigrants to Ontario, Canada. Canadian Medical Association Journal 182:781-789 DECODA study group. Age and sex-specific prevalence of diabetes and impaired glucose regulation in 11 Asian cohorts.(2003) Diabetes Care;26:1770-80 Forouhi NG, Sattar N, Tillin T, & McKeigue PM, Chaturvedi N.(2006) Do known risk factors explain the higher coronary heart disease mortality in South Asian compared with European men? Prospective follow-up of the Southall and Brent studies, UK. Diabetologia 49:2580–2588 Health survey for England 2004: The health of minority ethnic groups. Retrieved 28/7/2010 from http://www.ic.nhs.uk/webfiles/publications/hlthsvyeng2004ethnic/HealthSurveyForEngland161205_PDF%20.pdf Mukhopadhyay B, Forouhi NG, Fisher BM, Kesson CM, Sattar N(2006) A comparison of glycaemic and metabolic control over time among South Asian and European patients with type 2 diabetes: results from follow-up in a routine diabetes clinic. Diabet Med 23:94–98, Neel JV. Diabetes mellitus; a thrifty genotype rendered detrimental byprogress? (1962).American Journal of Human Genetics14:353-62. Stocker CJ, Arch JR, Cawthorne MA. Fetal origins of insulin resistance and obesity.(2005) Proc Nutr Soc;64:143-51 Southam L, Soranzo N, Montgomery SB, Frayling TM, McCarthy MI, Barroso I, Zeggini E. (2009) Is the thrifty genotype hypothesis supported by evidence based on confirmed type 2 diabetes- and obesity-susceptibility variants? Diabetologia 52:1846-1851 Read More