Epidemiological modelling of type 2 diabetes in Saudi Arabia :predicted trends and public health implications

Abstract

Background: The Kingdom of Saudi Arabia faces one of the highest prevalence rates of type 2 diabetes mellitus (T2DM) in the world. However, there are no credible local data on the trends and future projections of the disease, and the relevant international studies underestimated the true prevalence rates. This thesis used epidemiological modelling to study the trends in T2DM prevalence in Saudi Arabia, predicted its future levels, and quantified the impact of reducing some risk factors on the disease prevalence trends. Methods: This thesis developed and validated the “Saudi IMPACT Diabetes Forecast Model”, which integrates data on the population, obesity and smoking prevalence trends in Saudis aged ≥25 years to estimate the trends in T2DM prevalence (1992-2022) using a Markov modelling approach. The model considers different reasonable scenarios of future trends in obesity prevalence, and incorporates a number of parameters to model the disease epidemiology. These parameters include the estimated diabetes incidence, case-fatality, total mortality, relative risk of diabetes if obese, and relative risk of diabetes if a smoker. The model data inputs and parameters were obtained from different sources, including local departments, medical literature and assumptions. The model results were validated against local data from the STEPwise survey in 2005, and against the model of the Global Burden of Disease study, where the model produced reasonably close results to both of these studies. Results: The prevalence of T2DM among the Saudi population aged ≥25 years was estimated to rise substantially during the 30-year period of 1992-2022 from 8.5% to 39.5%, assuming some levelling off of obesity trends (capping), or to 44.1%, assuming uncapped increasing obesity trends. In men, T2DM prevalence was estimated to increase from 8.7% to 39.2% with capped obesity trends, or to 41.3% with continuing linear increase in obesity trends. In women, T2DM prevalence was estimated to increase from 8.2% to 39.8% with capping of obesity trends, or to 47.7% without such a capping. The model showed that if the trends in obesity start to decline by 10% in 12 years (2010-2022), a relative reduction of 13% in diabetes prevalence could be achieved. If the prevalence of obesity was halted at the 2010 levels, a 10% relative reduction in diabetes prevalence could be attained by 2022. ii Conclusion: T2DM is currently a major public health challenge in Saudi Arabia, and this thesis predicted that its burden will increase substantially in the next decade. Intensive and aggressive preventive measures directed to reduce the levels of risk factors, particularly obesity and smoking, can result in reasonable reduction of the disease prevalence, and therefore should be an urgent action.