Association of Socioeconomic Status With Risk Factor Target Achievements and Use of Secondary Prevention After Myocardial Infarction

Abstract

Importance: Low socioeconomic status (SES) is associated with poor long-term prognosis after myocardial infarction (MI). Plausible underlying mechanisms have received limited study.

Objective: To assess whether SES is associated with risk factor target achievements or with risk-modifying activities, including cardiac rehabilitation programs, monitoring, and drug therapies, during the first year after MI.

Design, setting, and participants: This cohort study included a population-based consecutive sample of 30 191 one-year survivors of first-ever MI who were 18 to 76 years of age, resided in the general community in Sweden, were followed up until their routine 11- to 15-month revisit, and were registered in the national registry Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies (SWEDEHEART) from 2006 through 2013. Data analyses were performed from January to August 2020.

Exposure: Individual-level SES by proxy disposable income quintile. Secondary exposures were educational level and marital status.

Main outcomes and measures: Odds ratios (ORs) with 95% CIs for achieved risk factor targets at the 1-year revisit and for use of guideline-recommended secondary prevention activities.

Results: The study comprised 30 191 participants (72.9% men) with a mean (SD) age of 63.0 (8.6) years. Overall, higher SES was associated with better target achievements and use of most secondary prevention. The highest (vs lowest) income quintile was associated with achieved smoking cessation (OR, 2.05; 95% CI, 1.78-2.35), target blood pressure levels (OR, 1.17; 95% CI, 1.07-1.27), and glycated hemoglobin levels (OR, 1.57; 95% CI, 1.19-2.06). The highest-income quintile was associated not only with participation in physical training programs (OR, 2.28; 95% CI, 2.11-2.46) and patient educational sessions (OR, 2.29; 95% CI, 2.12-2.47) in cardiac rehabilitation but also with more monitoring of lipid profiles (OR, 1.20; 95% CI, 1.08-1.33) and intensification of statin therapy (OR, 1.22; 95% CI, 1.11-1.35) during the first year after MI. One year after MI, the highest-income quintile was associated with persistent use of statins (OR, 1.26; 95% CI, 1.10-1.45), high-intensity statins (OR, 1.10; 95% CI, 1.00-1.21), and renin-angiotensin-aldosterone system inhibitors (OR, 1.27; 95% CI, 1.08-1.49).

Conclusions and relevance: Findings indicated that, in a publicly financed health care system, higher SES was associated with better achievement of most risk factor targets, programs aimed at lifestyle change, and evidence-based drug therapies after MI. Observed differences in secondary prevention activity may be a factor in higher long-term risk of recurrent disease among individuals with low SES.

Figure 1.. Associations Between Disposable Income Quintiles and 1-Year Risk Factor Target Achievements

Associations estimated with odds ratios (ORs) and 95% CIs in logistic regression models adjusted for age, sex, and calendar year. HbA_1c indicates hemoglobin A_1c (glycated hemoglobin); 53 mmol/mol is equivalent to 7.0% of total hemoglobin (to convert percentage of total hemoglobin to proportion of total hemoglobin, multiply by 0.01). ^aModerate or stronger exertion for 30 minutes, 5 times or more per week. ^bLDL-C indicates low-density lipoprotein cholesterol with a target lower than 100 mg/dL before 2012 or lower than 70 mg/dL after 2012 (to convert to millimoles per liter, multiply by 0.0259).

Figure 2.. Associations Between Disposable Income Quintiles and Use of Secondary Prevention Activities

Associations estimated with odds ratios (ORs) and 95% CIs in logistic regression models adjusted for age, sex, and calendar year. ^aIf reported symptoms of anxiety or depression at the 2-month revisit. ^bMeasured 2 or more times between index myocardial infarction and 1-year revisit; HbA_1c indicates hemoglobin A_1c (glycated hemoglobin). ^cAt any revisit. ^dIntensification refers to change of statin therapy intensity to higher category (none, low, moderate, or high) decided at revisits 2 months or 1 year after first myocardial infarction. Data derived from prescription claims in the national drug registry managed by the Swedish National Board of Health and Welfare. ^eIf left ventricular ejection fraction was lower than 40%. ^fIf left ventricular ejection fraction was lower than 40%, or diagnosis of hypertension or diabetes; RAAS indicates renin-angiotensin-aldosterone system.