Myocardial micro-alternation index (IMM) is one of the characteristics of the ECG dispersion mapping (DM) which is widely used for screening of the population. We studied the relationship between IMM, age and gender. We also investigated the prevalence of different IMM ranges: normal (<15 %, 15-21 % - boundary, >21 % - pathological) in visitors of the health centers (HC). Data of 537 820 visitors of the HC from 25 regions of Russia were analyzed. The visitors underwent ECG DM recording, anthropometry, measurement of blood pressure, glucose and cholesterol in capillary blood. The results have shown that IMM dependence on age and sex is very weak, so the special criteria are not required. The prevalence of IMM ranges («normal», «borderline values» and «pathology») is found to be age-dependent: the prevalence of pathological and borderline IMM values increased from 55 years and 35 years respectively. From the same age there is a decrease in the proportion of visitors with normal IMM values. The share of visitors with risk factors for non-communicable diseases is maximal among those whose values are in the IMM range considered as «pathology» and minimal in the range of «normal». © 2018 Stavropol State Medical University. All Rights Reserved.