Non-communicable chronic diseases are the leading cause of death worldwide, including Portugal, where they accounted for 86% of all deaths in 2016. Of these, cardiovascular disease is the main cause, responsible for 29% of all deaths.1 The latter also represents an important burden for the national health service, with more than 12 000 admissions per year in 2015 for myocardial infarction (MI).2

In recent decades, various preference-based instruments for measuring health-related quality of life (HRQoL) have been developed and validated in different countries. One such instrument is the EuroQol Five-Dimensional Questionnaire, Three-Level Version (EQ-5D-3L), developed by the EuroQol Group, validated for the Portuguese population and with published norms.3–7 Like many other diseases, cardiovascular disease can reduce patients’ ability to perform their usual activities, which will also have an economic impact. No studies have been published reporting HRQoL in a large populational sample of Portuguese patients with previous MI, although there have been several such reports for other diseases including rheumatoid arthritis, asthma, cataracts and chronic obstructive pulmonary disease.8

In 2011, a prospective population-based closed cohort study, the Epidemiology of Chronic Diseases (EpiDoC) study, was conducted in Portugal to estimate the national prevalence of rheumatic diseases, which also enabled the study of other non-communicable chronic diseases. A large population database was thus created for health-related research in Portugal, using a representative sample of the Portuguese population. This first wave of data collection was subsequently followed by two other waves, the last in 2015-2016. This included specific information on diagnoses of cardiovascular disease, enabling patients with previous MI to be identified. In this wave, HRQoL measurements were also obtained using the EQ-5D-3L instrument.

The main purpose of the present study was to assess HRQoL in patients with a previous self-reported MI and to explore the association between health status and sociodemographic variables.

In recent years, preference-based instruments have been increasingly used to measure HRQoL, particularly for cost-utility analysis. These instruments are indirect methods for measuring utilities that can be used to calculate quality-adjusted life years, as an alternative to more complex, time-consuming and costly direct methods of valuation. Because these instruments, particularly EQ-5D-3L, are easily and rapidly administered, their use has grown worldwide and they are now applied to almost all types of diseases.8 EQ-5D assesses health status and provides a measure of health for clinical and economic studies.3–5 Patients’ own reporting of their functional status, well-being and HRQoL has been rarely studied, particularly in Portugal. Such reporting is however important to inform decision-making by health policy makers and the medical community. By this means, patients can be directly involved in assessing the impact of MI on QoL. This type of analysis is also recommended in international guidelines on acute MI for evaluating quality of care.15

The estimated prevalence of previous MI in our study was 1.1%, which is slightly lower than in previous reports from the last National Health Surveys, applied in 2005/2006 and then in 2014, which were implemented jointly by the National Health Institute Doutor Ricardo Jorge and Statistics Portugal.16,17 The first survey reported 1.5% and the second 1.7%, but they used a broader term, “MI and its complications”, which thus probably includes other situations.

As expected, respondents with self-reported MI had a lower self-perception of their health status than those with no self-reported MI and the Portuguese general population. A ceiling effect was also observed, as was previously observed with this instrument in other types of populations.8 The health domains mostly affected were mobility and anxiety/depression. After MI, patients tend to reduce their activities. This is an important problem that should be addressed in comprehensive cardiac rehabilitation programs, but unfortunately these are not available for most patients with MI. Also, chronic diseases are frequently associated with anxiety and/or depression, and some patients might even require psychological support. The limitations in QoL found in the present study highlight the need for wider application of cardiac rehabilitation after MI, and this is indeed a class I recommendation in the European guidelines on MI.15 These programs include not only physical exercise but also nutrition counseling, close surveillance and control of all cardiovascular risk factors (including smoking cessation), and when necessary, psychological assessment and counseling.

As with many other conditions, the outcomes of chronic diseases are also affected by existing comorbidities, as we observed in the present study. This emphasizes the need for assessment of comorbidities in all studies dealing with HRQoL.

This study has some limitations that should be acknowledged. Firstly, possibly the main limitation is that MI was self-reported and therefore classification errors may arise. The same is true for other comorbidities that were also self-reported. It is sometimes difficult for an individual to clearly state whether they have a specific disease; particularly for MI, other types of cardiovascular disease might be incorrectly classified as MI by a layperson. However, the methodology we used for data collection was similar to that of other large population-based surveys, in which the collected data reflects the self-assessment that each person makes for the variable that characterizes her/his health status, with no clinical data available to confirm patients’ self-report. This population-based survey is in accordance with Commission Regulation (EU) No. 141/2013, the European Union regulation on statistics based on the European Health Interview Survey, which is a major requirement for enabling international comparisons of the results. This limitation could have been partly overcome by asking respondents specifically about different types of cardiovascular disease, such as MI, stable angina, arrhythmia, valve diseases, heart failure, hypertrophic cardiomyopathy and stroke, which could have helped to obtain more accurate information. Secondly, analysis of the associations between specific factors and HRQoL is limited by the cross-sectional nature of the study.

Adults with previous MI had a worse self-perceived health status and QoL. They assigned a lower self-perception to their health status in all domains, particularly in mobility and anxiety/depression, with a mean EQ-5D-3L index of 0.73, significantly lower than in patients without MI. Previous MI was not an independent predictor of health-related QoL after controlling for age, gender and associated chronic diseases.

No specific funding was obtained for the present manuscript. However, the original EpiDoC study received several sources of financial support. EpiDoC 1 and 2 were supported by grants from the Portuguese Directorate-General for Health and sponsorships from Fundação Calouste Gulbenkian, Fundação Champalimaud, Fundação AstraZeneca, Abbot, Merck Sharp & Dohme, Pfizer, Roche, Servier, Bial, D3A Medical Systems, Happybrands, Centro de Medicina Laboratorial Germano de Sousa, CAL-Clínica, Galp Energia, Açoreana Seguros and individual rheumatologists. EpiDoC 3 was supported by the Public Health Initiatives Programme (PT06) financed by the EEA Grants Financial Mechanism 2009-2014.

The authors have no conflicts of interest to declare.