The key results of this study are the strong associations between the number of cardiovascular diseases and disease burden, and the risk of poor global quality of life, poor physical function, poor role function, fatigue and dyspnoea. Among separate cardiovascular diseases, the highest risk of poor HRQoL appeared to occur in patients with angina and atrial fibrillation. Hypertension was the most common disease, but was not associated with decreased HRQoL.
Strengths of the study include the population-based design with random selection of participants, the high participation rate, and the large sample size. Moreover, HRQoL was measured with a well-validated and extensively used questionnaire. Of note is that among participants, fewer women reported cardiovascular disease than men, a possible effect of gender bias in diagnoses of cardiovascular diseases in society in general.
Limitations include uncertainty about the accuracy of self-reporting including the patient's own experience of disease and lack of validation of cardiovascular diseases, and the amount of missing data for cardiovascular disease (10%), and possible risk of higher non-participation among individuals with cardiovascular disease than among those without cardiovascular disease. Further, we lack information about time since diagnosis. It is possible that an association between cardiovascular disease and HRQoL varies with time since diagnosis. The number of participants with certain single cardiovascular diseases was limited, particularly those with heart failure, which reduced the statistical power to evaluate these conditions separately. Similarly, the findings of poor role function among the group with only atrial fibrillation has a wide CI and includes only a small number of participants, and therefore needs to be interpreted with caution. Nevertheless, the study revealed some strong effects that reached the level of statistical significance. In addition, the prevalence of cardiovascular diseases in the study cohort corresponds well with prevalence observed in the Swedish population,19
indicating validity and generalisability of the results to age groups included in the study. However, the HRQoL questionnaire used was constructed for, and has mainly been validated in, cancer patients and might not be an ideal measurement to assess HRQoL in people with cardiovascular disease. In using a potential non-sensitive measure of HRQoL the study may not be able to correctly determine the threshold for reporting poor HRQoL instead of good HRQoL associated with cardiovascular disease. Therefore, we chose cut-offs based on responses that would be likely to capture a clinician's attention, for example, a patient responding ‘quite a bit’ or ‘very much’ for a symptom or function, instead of using mean score differences between groups.
To the best of our knowledge, only one previous study has presented findings about HRQoL differences between people with and without cardiovascular disease in a random sample of a general population. In line with the present results, this study concluded that health state utility values differ (except for by age and gender) by history of cardiovascular disease including number of cardiovascular disease. Associations between cardiovascular disease and HRQoL have mainly been assessed using other designs. One hospital-based cross-sectional study assessed patients with an acute episode of coronary heart disease and compared their HRQoL to that of the Spanish general population. It showed that the coronary heart disease patients, especially the youngest patients, reported lower role function, more pain, poorer vitality and social functioning, than the general population.7
However, this study only included 132 patients and was performed during the acute phase of the disease. A study from the UK, set in two hospitals, compared HRQoL in patients 4 years after a myocardial infarction with population norms and found similar results.9
A study from the USA found an association between the number of comorbidities and poor HRQoL.20
Similarly, in a diabetic population, cardiovascular disease was found to have a negative effect on HRQoL.3
Thus, the results of the present study and the existing evidence suggest a substantial negative effect of cardiovascular disease on several aspects of HRQoL.
One biological explanation for poorer HRQoL among participants with a greater number of cardiovascular diseases is that each disease may result in a certain load of symptoms that, when experienced together, cause a negative synergetic effect on HRQoL.11
Another possible explanation is that patients with more cardiovascular diseases are more likely to have other unknown comorbidities than those we have assessed, or temporary diseases not captured by the questionnaire that may have an impact on HRQoL. However, our results were adjusted for other self-reported comorbidities (open question, free text response). The higher risk for poor HRQoL observed among participants with angina or atrial fibrillation may be due to the nature of these diseases. For example, pain associated with angina or tachycardia from atrial fibrillation, may contribute to greater limitations, or act as a constant reminder of the disease, and therefore exert a stronger influence on HRQoL. In contrast, conditions such as hypertension are of a more ‘silent’ or asymptomatic nature but could affect HRQoL via medications and their possible side effects. Furthermore, myocardial infarction patients may view their disease as a onetime occurrence that happened in the past. If patients recover fully, this may contribute to the disease having a lower impact on their HRQoL.
The findings of this study, that both the number of cardiovascular diseases and the subjective burden of disease, affect HRQoL, are important for the care of patients. It seems that patients’ own perceptions of their disease, which might be different from a clinician's rating of their disease, have a strong influence on HRQoL. HRQoL assessments could be used as a helpful complement to a clinical assessment to give a comprehensive view of a patient's condition.21
The strong association between major burden of any cardiovascular disease and poor HRQoL, in particular poor physical function and symptomatic fatigue and dyspnoea supports the idea that HRQoL may reflect objective symptoms from cardiovascular disease. These findings suggest that a general question about the subjective burden of disease may be useful within the clinic, since patients reporting minor burden are less likely to suffer negative impact of the disease on their daily life, while those reporting major burden might need a more thorough review of the impact of their disease. However, further evaluation of the partial overlap between subjective ratings of burden and HRQoL is needed as a greater number of objective symptoms do not necessarily equate poor HRQoL since patients may prioritise other values or aspects or adopt coping strategies which may also influence HRQoL.
In conclusion, this large, population-based study of unselected people aged 40−79 years with and without cardiovascular diseases in the general Swedish population, indicates that people with several cardiovascular diseases and people reporting a subjective larger burden of cardiovascular diseases are at a substantially increased risk for poor HRQoL indicating a need for more intense follow-up and interventional care of their cardiovascular diseases.