Type 2 diabetes mellitus in transitional Thailand:incidence, risk factors, mediators, and implications

Abstract

Background Economic growth in Asia is changing population health profiles. Family structures, environments, occupations, education, and health behaviours have also changed and science-based health services have evolved. As part of this ‘health-risk transition’, noncommunicable diseases including type 2 diabetes mellitus (T2DM) have emerged. While the major causes of the diabetes epidemic in western, high-income countries are well documented, little is known of T2DM in developing Asia. The knowledge gap includes Thailand, which needs to identify local factors driving its T2DM epidemic.

Aim This thesis aims to better understand the epidemiology of T2DM emerging in Southeast Asia.

Methods Participants were from the Thai Cohort Study (TCS) of the health-risk transition. They were distance-learning adult students living all over Thailand, enrolled at Sukhothai Thammithirat Open University, and surveyed in 2005, 2009, and 2013 using mailed questionnaires that covered socio-demographic characteristics, lifestyle behaviours and self-reported health outcomes. In addition to these data, physician telephone interviews were conducted to validate self-reported questionnaire responses (2015); and a dietary survey was conducted to assess transitional dietary patterns (2015).

Multiple logistic regression was used to calculate odds ratios and 95% confidence intervals (CIs) for longitudinal associations between exposures of interest and T2DM. Non-linear associations of body mass index (BMI) and T2DM were modelled using restricted cubic splines. Counterfactual mediation analysis explored sugary drink linkage to T2DM. Population attributable fractions and potential impact fractions were calculated. Principal component analysis identified dietary patterns and multivariable linear regression produced standardized coefficients and 95% CIs for associations between socio-demographic measures and dietary pattern scores.

Results Physician telephone interviews of a cohort sample demonstrated high validity of questionnaire self-reported doctor diagnosed T2DM suggesting that self-reported doctor diagnosed T2DM is a feasible and acceptable method for assessing diabetes in epidemiological studies.

Overall eight-year T2DM incidence was 177 per 10 000 (95% CI 164-190) with higher incidence in men. For both sexes, factors most strongly associated with T2DM risk were greater age and BMI. Two-thirds of all T2DM cases could be attributed to overweight and obesity. T2DM risk increased at BMI levels <23kg/m2. The increasing T2DM risk associated with body size became statistically significant at a BMI of 22 kg/m2 and 20 kg/m2 in men and women, respectively. For both sexes, living in urban areas increased T2DM and risk of consuming unhealthy dietary patterns, while a higher income associated with healthy dietary patterns. In Thai men, smoking and alcohol consumption increased T2DM risk. In women, sugary-drink consumption increased T2DM risk, of which 23% was mediated through obesity. In men, income and education were associated with increased T2DM risk. In women, education protected against unhealthy dietary intake. Overall, women tended to have safer behaviours (e.g. low prevalence of smoking and alcohol consumption) and better outcomes (e.g. lower prevalence of obesity and lower rates of T2DM).

Conclusions Findings from young to middle-aged, educated Thai adults nationwide show that selfreport of incident T2DM is a valid method for assessing diabetes in epidemiological studies, T2DM incidence in Thailand is high, and accompanying lifestyle and sociodemographic transitions are driving the T2DM epidemic. Thai men are likely to be in the middle stages of the health-risk transition while women are more advanced. Health-risks for T2DM are changing substantially and could be modified. These risks need to be targeted to prevent and control diabetes in Thailand. Show more