Background: Qatar—an Arabian Gulf country with the highest per capita income in the world—has the tenth highest diabetes mellitus prevalence worldwide (16.7%). Prevalence of obesity, active smoking, and physical inactivity are reported as being 41.4%, 16.4%, and 45.9%, respectively. It is therefore critical to assess the future burden of type 2 diabetes mellitus (T2DM) in Qatar and its risk factor drivers.
Aims: To develop and demonstrate a novel mathematical modelling approach to forecast the burden of T2DM and to investigate its epidemiology for the purpose of informing public health policy and programming. 
Method: A population-level compartmental mathematical model was constructed and applied to Qatar. The model was stratified according to sex, age group, risk factor status, and T2DM status, and was parameterized by nationally-representative population-based data, including demographic, epidemiological, and cost data. The model disaggregates the population into 20 age groups, with each group representing a five-year age band and incorporates four main susceptible classes: healthy (i.e. non-obese, non-smoker, physically active, and non-diabetic), obese, smoker, and physically inactive. The model accounts for overlaps between risk factors by further stratifying the susceptible population into compartments with overlapping risk factors. Spending attributed to T2DM of Qatar’s total health expenditure was estimated based on per capita health expenditure. The effect of the risk factors on T2DM was estimated by calculating the total T2DM incident cases attributed to each of the risk factors through population attributable fraction approach. Sensitivity and uncertainty analyses were conducted to assess the robustness of the findings.
Results: T2DM prevalence was predicted to increase from 16.7% in 2012 to at least 24.0% by 2050. The rise in T2DM was most prominent in age groups 45-49 and 50-54 years. T2DM health expenditure was estimated to increase by 200-600% and to account for up to 32% of total health expenditure by 2050. Prevalence of obesity, smoking, and physical inactivity was predicted to increase from 41.4% to 51.0%, from 16.4% to 19.4%, and from 45.9% to 53.0%, respectively by 2050. The proportion of T2DM incidence attributed to obesity, smoking and physical inactivity was estimated at 57.5%, 1.8%, and 5.4%, respectively in 2012, and 65.7%, 2.1%, and 6.0%, respectively by 2050. Exploring different scenarios for the trends in T2DM-related risk factors, T2DM prevalence could potentially reach as high as 37.7% by 2050. Sensitivity and uncertainty analyses affirmed the validity of our predictions.
Discussion: Using our innovative modelling approach, a rising T2DM epidemic in Qatar was predicted to continue in the next three decades, driven by population growth, ageing and adverse trends in risk factors. Obesity was found to be the principal risk factor explaining over half of T2DM incidence. T2DM must be a national priority addressed by preventive and therapeutic interventions targeting T2DM and its modifiable risk factors. We applied the model to Qatar, a high-burden T2DM country, but the approach is general and can be applied broadly across countries.

Forecasting the burden of type 2 diabetes mellitus in Qatar to 2050: a novel modeling approach