The global prevalence of myocardial infarction: a systematic review and meta-analysis

1Myocardial Infarction (MI) is one of the life-threatening coronary events with SCD and the most severe clinical presentation of coronary artery disease (CAD). This pathology is divided into two categories of ST-elevation MI (STE-MI) and non-ST-elevation MI (NSTE-MI). Since unstable angina is the imminent background for MI, it is also considered an acute coronary syndrome (ACS) status.

2More than 3 million individuals develop STE-MI each year, and more than 4 million people represent STE-MI pathology. Although MI is mainly detected in developed countries, it is also detected commonly in developing countries. In a published study with 19,781 CAD patients, the MI prevalence was found 23.3%. In recent years, a considerable decreasing trend in STE-MI incidence was detected in European countries and the United States.

3MI is the main cause of human death, globally. Although the global rate of MI-associated mortality was totally decreased, the incidence of heart failure (HF) is at a high level. The mortality and morbidity rates are high in MI-related HF. HF induces detrimental impacts on the healthcare systems of the United States, affecting 6 million individuals, 300,000 deaths per year, and approximately $40 billion in costs. Also, the economic impact of MI is at a high rate. In 2010, more than 1.1 million hospitalizations following MI attacks were reported in the United States, with an estimated direct cost of $450 billion. Body weakness is a common complication in cardiovascular diseases and is also a common syndrome among the elderly causing weight loss, fatigue, physical manipulation, decreased walking speed, and low body activity. Obesity, sedentary lifestyle, hypertriglyceridemia, or inflammation markers (such as high-sensitivity C-reactive protein [hs-CRP]), are mostly independent cardiovascular (CV) risk factors associated with insulin. Various published articles represented a general increase in the prevalence of cardiovascular risk factors (especially diabetes, cholesterol and obesity, and even smoking). In MI patients < 55 years, smoking was found a unique cardiovascular risk factor in 80% of cases.

4The present systematic review and meta-analysis study seems beneficial for health system policymakers requiring the prevalence of MI patients during the allocation of health care resources. We believe that elimination of the complications and reduction in mortality rate need comprehensive assessment approaches.

5In this study, the primary search was conducted on June 6, 2022. Databases of PubMed, Web of Science, ScienceDirect, Scopus, Embase, and Google scholar search engine were hired for definition of searching strategy. Also, the main keywords of “Prevalence”, “Outbreak”, “Burden”, “Myocardial Infarction”, “Myocardial Infarct”, and “Heart Attack” were used for comprehensive searching with no time and language-associated restrictions. Following paper selection, the related citations were imported to the information management software (EndNote v.8x). Finally, in order to secondary screening, all citations of the collected articles were reviewed manually. The searching was also updated on September 13, 2022.

6All gathered studies reporting the MI prevalence, available full texts, and studies with sufficient data (number of samples, percentage of MI prevalence) were totally included in this study. Also, case–control studies, cohort investigations, case series, case reports, reviews, repetitive papers, studies with insufficient data, papers with unavailable full texts, and conference studies were excluded.

7The Endnote software (v. X8) was hired to organize the selected studies. Duplicate studies were detected and merged together. In primary screening, irrelevant studies were removed following assessment of the titles and abstracts. Then, the full texts of the remaining articles were screened according to the inclusion and exclusion criteria. All screening protocols were conducted by two independent authors in order to accelerate the credibility index and inhibit the potential searching bias. Corresponding author was also responsible for the management of possible disagreements among the researchers. Finally, 33 studies were included for quality control assessment.

8For validation and the quality control assessment, an observational study-associated checklist (The Strengthening the Reporting of Observational Studies in Epidemiology checklist (STROBE)) was used. This STROBE checklist consisted of six assessment scales of Title, Abstract, Introduction, Methodology, Results, and Discussion with 32 evaluation items including Title, Problem Statement, Study Objectives, Type of Study, Statistical Population, Sampling Method, Appropriate Sample Size Determination, Variables Definition, and the Procedures, Data Collection Tools, Statistical Analysis Methods and Findings. The article with STROBE scoring ≥ 16 was considered good and moderate (included in the study), and articles < 16 were poor quality (excluded from the study).

9The eligible data were extracted by two researchers based on the previously prepared checklist (containing the Author's name, Year of publication, Research region, Sample size, Disease prevalence, and Age).

10The heterogeneity of the studies was assessed using I2 test. Also, the Egger test was used for publication bias assessment. All statistical analysis was applied in Comprehensive Meta-Analysis software (Version 2).

11Whole eligible data (6462 studies systematically and 134 investigations manually) regarding the prevalence of MI were collected based on the PRISMA guideline and categorized into two groups of individuals < 60 and ≥ 60 years. All the papers were imported into the information management software (EndNote v.X8). Among the total number of 6596 studies, 4566 duplicate investigations were detected and merged together. During the primary screening, the Title and Abstract of the remaining studies were assessed. Subsequently, 1879 investigations were excluded due to the irrelevant contents. Following the secondary screening, the full texts of the papers were assessed (118 studies were also excluded in this stage). Eligible collected papers were assessed based on the STROBE checklist, and the studies with poor-quality methodology were removed from the investigation. Finally, 32 high-quality papers were included for systematic review and meta-analysis study (Table 1) (Fig. 1).

12Data analysis of 20 eligible studies with a sample size of 5.071.185 individuals > 60 years was conducted, and I2 index represented a high heterogeneity rate (I2 = 99.7%). Meta-analysis assessment revealed that the global prevalence of MI in individuals > 60 years was 9.5% (95%CI: 7.7–11.6) (Fig. 2). Also, no publication bias (p = 0.113) was found in this age group (Fig. 3). Following data analysis of 22 eligible studies with a sample size of 29.826.717 individuals < 60 years, the I2 index showed a high heterogeneity rate (I2 = 99.9). The global MI prevalence in this age group was found 3.8% (95%CI:2.7–5.3) (Fig. 4). Also, no publication bias (p = 0.064) was detected (Fig. 5).

13This systematic review and meta-analysis study in the first investigation examine the global prevalence of MI in two groups of individuals < 60 and > 60 years. The global prevalence of MI < 60 years was detected 3.8% according to 22 studies with a sample size of 29.826.717 individuals. This value was also found 9.5% in the remaining 20 studies with a sample size of 5.071.185 patients > 60 years.

14Following gender categorization, the prevalence of MI in males was found almost 5 folds greater than the females. In a large number of other published studies, a high prevalence of MI was reported in males (> 60%) compared to females. On the contrary, other literature reported higher MI prevalence in females, probably due to the sedentary lifestyle, metabolic syndrome, and similar risk factors.

15Based on the geographical distribution, there were different results representing the MI prevalence including 10.4%, 0.1%, 0.2%, and 2.5% in Sudan, Senegal, Nigeria, and Kenya, respectively. These geographical differences in MI prevalence were probably associated with lifestyle, disease prevention plans, and the level of availability of medical diagnosis resources.

16Extracted data from a large, diverse, community-based population represented a considerable decrease in MI prevalence (after 2000) and incidence of ST-segment elevation (in recent decades). Although the statistical analysis of CAD prevalence and the related mortality rate showed a decremental trend, the statistics of published literature (before 2002) had no report.

17Various studies conducted in the United States (after 2000) revealed a considerable decremental trend in the incidence of AMI and the rate of hospitalization. The rate of AMI incidence also decreased in Sweden between 2001 to 2008 which was higher in males. A similar trend conducted in the Netherlands from 1998 to 2007 also reported the same results. Respectively, 33% and 31% reduction of AMI rates in males and females were reported in England (2002 to 2010). Another study showed a steady decline in AMI and mortality rates in most regions of Europe. This study was consistent with the findings of the present investigation reporting that a reduction in MI prevalence was probably associated with innovation of preventive medical protocols and a parallel improvement in risk factors management.

18The prevalence of angina and MI decreased considerably over the 12-year period. The reduction in the prevalence of cardiovascular diseases (CVD), including angina and MI, may result from application of preventive medical procedures and management of risk factors. On the contrary, a high prevalence of undiagnosed MI (26.9%) was also reported. Consequently, more participants (17%) had un-diagnosed MI, and others (9.6%) represented diagnosed MI. In another study, the incidence of definitive MI diagnosis in hospitalized patients was 272/100,000 individuals (aged 30–74).

19The high rate and increased severity of CAD in patients with a family background were directly related to the risk of MI in younger ages and both genders. The scientists also found that cocaine addicts are 7 times more at risk of heart attack. Notably, an increased rate of MI incidence was detected in people < 55 years during 1997–2005. In parallel, various studies reported an annual increase (4%) in the incidence of AMI among women aged 35 to 54 years in Western Australia (from 1996 to 2007) and an increase among women aged 20 to 49 years (from 1994 to 2004). In these studies, the accelerated prevalence of smoking (especially among young females), obesity, and the lack of physical activity have been reported in adolescents and young adults.

20In this study, a higher prevalence was reported in people over the age of 60. In the results reported in the global epidemiology study of ischemic heart disease, which was based on the results of the global burden of disease study, it was reported that ischemic heart disease has a high upward trend with It shows increasing age and the growing trend continues until the age of 89.

21Since the age range explained in published studies had no similarity to the age groups in the present study, some eligible papers were excluded. Although, almost half of the studies were conducted in specific subpopulations (such as other heart disease and diabetic patients admitted to the emergency department); difficult conclusions regarding the MI prevalence in general population were possible.

22According to the findings of the present study, the prevalence of MI in people < 60 and > 60 years old were 3.8% and 9.5%, respectively. Therefore, based on the results of the studies that have been reviewed and included in the meta-analysis, the high prevalence of MI was reported to be higher in individuals > 60 years which is considered a warning for health policymakers regarding the importance of this age for diagnosis and screening procedures of MI.