Our finding that women had lower HRQoL than men at T1 and T2 is consistent with other research on short-term recovery from MI [10, 13, 19, 21, 29]. Like the majority of earlier studies we observed gender differences in both components of HRQoL, however Bogg21 found that women scored lower only on emotional HRQoL. Also like other studies of longer-term recovery [7–9] we found that gender difference in HRQoL were no longer present 1 year after MI.
We found that the factors shaping HRQoL after MI are influenced by both gender and time. There were fewer predictors of symptoms in women; neither clinical nor psychosocial factors predicted women’s HRQoL during short-term recovery and the reasons for this remain unclear [30]. As in a previous study [31] neither age, comorbidities nor characteristics of MI predicted HRQoL and unlike the earlier study [31] neither employment nor marital status were predictors in our sample. After controlling for variance in symptoms at T1, substance use at T2 and resignation at T2 predicted T3 symptoms. This can be interpreted as a suppression effect32 and confirms the complexity of HRQoL correlates.
In men the predictors of symptoms at T1 and T2 were almost identical: being professionally active before MI was a negative predictor, whereas angina at T1 and trait anger were positive predictors. At T2 we also observed a delayed, negative effect of pre-MI duration of angina on HRQoL. One year after cardiac rehabilitation angina positively predicted symptoms in both genders and also positively predicted discomfort in women.
We found that, with a few exceptions, predictors of discomfort were gender-specific and time-dependent. In women trait curiosity and education level were negative predictors of discomfort at T1 or T2 or both, whereas resignation at T1 was a positive predictor of discomfort at T1 and T2. In both men and women, however, trait anxiety and use of anxiolytics were negatively related to HRQoL at T1 or T2 or both. In men we observed that optimism was a negative predictor of discomfort at T1 and T2. At T3 there were several gender differences in predictors of discomfort. T3 discomfort was positively predicted by two clinical variables in women (use of beta-blockers at T1 and angina at T3) and substance use at T2, whereas in men it was negatively predicted by problem solving at T1 and positively predicted by resignation at T3.
As in other studies [29, 33, 34], pre-MI angina and current angina symptoms were related to HRQoL at various stages of recovery. One year after MI nearly 20% of survivors still experience angina [35] and it can reduce patients’ HRQoL at one-year follow-up and later [36]. However, in our study angina in men (pre-MI, at T1 and at T3) predicted symptoms at all timepoints, whereas in women the only relationships were between angina at T3 and symptoms and discomfort at T3.
Our results show that pharmacological treatment also plays an important role in HRQoL. However, our finding that in women use of beta-blockers at T1 was associated with higher discomfort at T3 is not consistent with other research. Arendarczyk [37] found that use of beta-blockers two years after MI was positively associated with HRQoL, whereas another study found that use of beta-blockers exacerbated functional decline in older nursing homes residents with cognitive impairment [38]. Use of anxiolytics at T1 positively predicted discomfort in both genders at the earlier timepoints, indicating that emotional disturbance after MI may affect HRQoL in both men and women [6].
It is interesting that men’s employment status predicted both aspects of their HRQoL at early timepoints, whereas in women education predicted discomfort at T1 and T2. The positive effect of education on HRQoL has been observed in several studies of men [6], but not in research on women [31]. The gender-specific effect of employment in our sample may reflect the fact that the men were more likely to have been professionally active before MI than the women. In Poland women retire 5 years earlier than men and tend to be less professionally active [39]. Being employed before MI increased the chance of returning to professional activity, which has been shown to reduce emotional distress [40]. We observed a fall in the proportion of men employed at T3, which may have contributed to the deterioration in men’s HRQoL. Working less or not working one year after MI have been related to depression and lower health status [41].
After controlling for variance in HRQoL at T1 we noticed some changes in the T2 outcomes in both genders, with HRQoL at T1 emerging as the strongest predictor of HRQoL at T2. Controlling for HRQoL at T1 and T2 (when there were gender differences in HRQoL) hardly affected outcomes at T3. In other words, HRQoL at one timepoint predicted HRQoL at later timepoints, provided the interval was short. Another study has also reported that HRQoL at one timepoint predicted HRQoL 6 months later [31].
Our data suggest that there are gender differences in the psychosocial determinants of HRQoL. Personality only predicted HRQoL at early timepoints. Psychosocial discomfort was negatively predicted by openness to novelty (trait curiosity) in women and by expectancy of a good future (optimism) in men. In our sample trait curiosity was lower in women, but there was no gender difference in optimism. Some studies have shown that self-efficacy [42] and sense of coherence [17] predict HRQoL six months or one year after MI. Sense of coherence was a stronger predictor of HRQoL dimensions one year after MI in women than men.
It should also be noted that although there was no gender difference in trait anger in our sample, it only predicted HRQoL in men. Anger, hostility and aggression have long been recognised as risk factors for the onset and progression of coronary heart disease [43]. It has also been shown that there is a strong negative association between anger and mental HRQoL when controlling for effects of gender, age and functional status [44]. However, a study of women with coronary heart disease found that trait anger was not related to any aspect of HRQoL [31].
Trait anxiety positively predicted discomfort in both genders, which is in line with other studies [45] showing the negative relationship between state anxiety and HRQoL in cardiac patients during long-term recovery [46].
Ways of coping, although seen as important contributors to HRQoL [47], are not often investigated in this context [31, 45]. It is assumed that gender differences in coping, for example women’s more frequent use of disengagement strategies [20, 48] and their tendency to use a greater variety of coping strategies [21] may account for gender differences in HRQoL. However Brink [19] observed no gender differences in using the coping strategies after MI.
We observed that resignation predicted HRQoL at T1 and T2 in women and at T3 in men. However, in our sample there was no gender difference in the dynamics of use of this strategy, although women made more use of resignation than men at T2 [28]. This shows that even when there is no gender difference in use of a coping strategy, there may be a gender difference in how it is related to HRQoL. Another important observation relates to delayed effects. In men, but not women, problem solving at T1 predicted T3 discomfort; there was no gender difference in the dynamics of this strategy, although there was a main quadratic effect of time for the whole sample, reflected in an increase in use of problem solving at T2 [28]. It appears that in men applying problem solving strategies during early cardiac rehabilitation has a delayed effect on HRQoL. Unfortunately, the delayed positive effect of problem solving is counterbalanced by a negative effect of resignation at T3. We also observed that substance use at T2 was a delayed positive predictor of T3 discomfort in women; there were no gender or time differences in use of this strategy [28]. In women substance use at T2 was negatively related to T2 symptoms, after controlling for variance in symptoms at T1. This suggests that using prescribed or over-the-counter medication to help one to forget about problems and to console oneself produces a short-term reduction in physical symptoms, but increases psychosocial discomfort in the long term, perhaps because it contributes to unrealistic expectations or is associated with unforeseen deterioration in physical condition. These speculations about indirect relationships need to be verified in further research.
Limitations of the study
Our indicator of HRQoL was a specially developed transformation of NHP scores, which may not be strictly comparable with other HRQoL measures used in cardiac studies, although the content is similar. However, this generic tool makes it possible to draw comparisons with other clinical groups. In an attempt to restrict the number of predictors in the model to an acceptable number (less than number of observations divided by 10), we adopted a two-step selection procedure. Although women constituted approximately 30% of the sample, we achieved this excepting analysis of men at T3. The proportion of women was very similar to that in other mixed gender samples [7, 10, 13], but the absolute number of women in the sample was relatively small.
The groups were homogeneous with respect to almost all socio-medical characteristics, with the exceptions of employment status and intensity of rehabilitation training. This may be partially responsible for a small number of the effects we observed. We did not measure some probable determinants of HRQoL, for example post-menopausal symptoms [14], level of depression [13] and health-related behaviours [6]. We recommend that future studies use a broader or different selection of predictors.