Socioeconomic status and ethnic variation associated with type 2 diabetes mellitus in patients with uncontrolled hypertension in Singapore

INTRODUCTION: The burden of type 2 diabetes mellitus (T2DM) and related vascular complications is particularly high in Asians and ethnic minorities living in the West. However, the association of T2DM with socioeconomic status (SES) and ethnicity has not been widely studied in populations living in Asia. Therefore, we investigated these associations among the multiethnic population with uncontrolled hypertension in Singapore. RESEARCH DESIGN AND METHODS: In a cross-sectional study using baseline data of a 2-year randomized trial in Singapore, we obtained demographic, SES, lifestyle and clinical factors from 915 patients aged ≥40 years with uncontrolled hypertension. T2DM was defined as having either: (i) self-reported ‘physician-diagnosed diabetes confirmed through medical records’ or taking antidiabetes medications, (ii) fasting blood glucose levels ≥7.0 mmol/dL or (iii) hemoglobin A1c ≥6.5%. The SES proxies included education, employment status, housing ownership and housing type, and the ethnicities were Chinese, Malays and Indians. Logistic regression analyses were used to evaluate the association of T2DM with SES and ethnicity. RESULTS: Higher proportion of T2DM was observed in Malays (40.0%) and Indians (56.0%) than Chinese (26.8%) (p<0.001), and in patients with lower SES (ranging from 25.7% to 66.2% using different proxies) than those with higher SES (19.4% to 32.0%). In a multivariate model comprising age, gender, ethnicity and SES, Malay ethnicity (OR 1.59; 95% CI 1.04 to 2.44, p=0.031) or Indian ethnicity (OR 3.65; 95% CI 2.25 to 5.91, p<0.001) versus Chinese and housing type (residing in one to three rooms (OR 2.00; 95% CI 1.16 to 3.43, p=0.012) or four to five rooms public housing (OR 1.86; 95% CI 1.13 to 3.04, p=0.013) vs private housing) were associated with higher T2DM odds. The associations of Indians and one to three rooms public housing with T2DM met the significance after accounting for multiple testing (p≤0.0125). CONCLUSION: Our study suggests that housing type and ethnic variation are independently associated with higher T2DM risk in patients with uncontrolled hypertension in Singapore. Further studies are needed to validate our results. TRIAL REGISTRATION NUMBER: NCT02972619.