National trends in mortality attributable to metabolic risk factors in Iran

Abstract Background Cardiovascular disease is the number one non-communicable cause of mortality. Body-mass index (BMI), fasting plasma glucose (FPG), total cholesterol (TC), and systolic blood pressure (SBP) are known predisposing risk factors. In this paper, we aimed to estimate the changes in mortality attributable to these factors in Iran. Methods Three consecutive national non-communicable diseases surveillance surveys were used to estimate the mean and SD of metabolic risk factors at national and provincial levels from 2005 to 2011. The surveys included 89 400, 30 000, and 12 400 individuals aged from 15 to 65 years, selected by multilevel cluster sampling in rural and urban levels in 2005, 2007, and 2011, correspondingly. For people above 65 years of age, the mean and SD of metabolic risk factors were imputed using the pooled data of 47 health studies around the world. The effect size of each risk factor on mortality was obtained from the previous meta-analyses in systematic reviews. The population-attributable fraction was calculated based on theoretical minimum risk exposure distribution (BMI 21 kg/m2 [SD 1·0], SBP 115 mm Hg [SD 6·0], TC 3·8 mmol/L [SD 0·6], and FPG 4·9 mmol/L [SD 0·3]) as an alternative exposure distribution. Death-specific mortality numbers based on sex and age were derived from the national death registry using synthetic extinct generation methods to correct for incompleteness. A comparative risk assessment was performed to estimate the deaths attributable to the risk factors. Findings From 2005 to 2011 SBP-attributable death increased from 41 000 (95% uncertainty interval 38 000–44 000) to 44 243 (40 149–48 337) in males and 39 000 (36 000–42 000) to 42 171 (38 351–45 991) in females. Likewise, BMI mortality rose from 13 000 (11 000–15 000) to 24 275 (20 393–28 157) in males and 17 000 (14 000–20 000) to 30 843 (25 859–35 827) in females. FPG-attributable mortality was also increasing from 2007 to 2011, but TC did not follow this pattern, and instead fell slightly. Interpretation Although SBP is still the leading cause of cardiovascular mortality, BMI has the most accelerated trend slope. BMI follows SBP as the main target of intervention strategies. Funding The Non-Communicable Diseases Research Center (NCDRC) at the Tehran University of Medical Sciences and the Endocrinology and Metabolism Research Center (EMRC) at the Tehran University of Medical Sciences, Tehran, Iran.