The levels and trends of raised total cholesterol at national and sub-national scale in Iran from 1990 to 2016: systematic review and pooled analysis

Raised serum cholesterol is a main risk factor for all-cause and cardiovascular-attributable mortality and morbidity in all nations, particularly in developing countries. Effective policy making in this regard requires detailed data to distinguish disparities and specific patterns. Thus, we aimed to estimate the level and trends of serum cholesterol level and raised total cholesterol prevalence at subnational level from 1990 to 2016 in Iran.We conducted a comprehensive systematic review, through which we detected nine national surveillances, seven large-scale population-based studies, and 88 studies published in databases. We conducted a two-stage model: an Age-Spatio-Temporal model and a Gaussian Process Regression to estimate mean total cholesterol (TC). We used crosswalk to estimate prevalence of raised total cholesterol based on estimated mean, defined as TC higher than 200 mg/dL. All estimations were done in subgroups with sex, age, year, and province combinations.At national level, the number of adults with raised total cholesterol decreased from 10·5 (9·8 – 11·5) million (5·2 million in women) in 1990 to 9·9 (9·0 – 10·6) million (5·4 million in women) in 2016. Age standardized prevalence of raised total cholesterol at national level has decreased from 57·2% (95% CI: 53·3 – 61·1) to 22·4% (20·5 – 24·3) in women and from 53·2% (49·1 – 57·3) to 18·0% (16·4 – 19·6) in men between 1990 and 2016. From 1990 to 2016, age standardized mean TC in both men and women has decreased from 197·3 mg/dL (186·1 – 209·4) to 168·5 (160·7 – 176·7) and from 202·5 mg/dL (191·2 – 214·6) to 174·5 mg/dL (166·6 – 182·8), respectively. In both sexes, population growth had the highest contribution to increase in number of adults with high TC.Decrease in raised TC is likely the result of statin widespread use, food industry improvements, and the expanded primary health care of the country. Provided data at subnational level would help with further evidence-based and population-specific policy making to ensure the continuation of this successful experience, particularly targeting inter-gender and inter-provincial differences. Finally, the increased number of adults with TC slightly below the 200 mg/dL cutoff is threat for the healthcare that should be systematically managed.