Psychosomatic Medicine 67:59-63 (2005)
© 2005 American Psychosomatic Society
Psychologic Distress in Postmyocardial Infarction Patients Who Have Returned to Work
Chantal Brisson, PhD,
Richard Leblanc, PhD,
Renée Bourbonnais, PhD,
Elizabeth Maunsell, PhD,
Gilles R. Dagenais, MD,
Michel Vézina, MD,
Benoît M
sse, PhD and
Edeltraut Kröger, MSc
From the Unité de recherche en santé des populations, Québec, Canada (C.B., R.L., E.M.); Université Laval, Québec, Canada (C.B., R.B., E.M., M.V., E.K.); Institut de cardiologie de Québec, Québec, Canada (G.R.D.); and Fred Hutchinson Cancer Research Center, Seattle, Washington (B.M.).
Address correspondence and reprint requests to Chantal Brisson, PhD, Unité de recherche en santé des populations, Centre hospitalier affilié universitaire de Québec, Hôpital Saint-Sacrement, 1050 Chemin Sainte-Foy, Québec, Québec, Canada G1S 4L8. E-mail: cbrisson{at}uresp.ulaval.ca
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ABSTRACT
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Objective: To assess the prevalence of psychologic distress in women and men returning to work after a myocardial infarction (MI) and to compare this prevalence with the prevalence observed among men and women of the general working population.
Methods: The study population was composed of 990 post-MI patients (106 women and 884 men) recruited in 30 hospitals who had returned to work after their first MI. Psychologic distress was measured with the French version of the Psychiatric Symptom Index (PSI). Adjusted mean PSI score and prevalence of psychologic distress were compared with those observed in 8829 other workers (3823 women and 5006 men), representative of the general working population.
Results: Mean PSI score was higher in post-MI women (30.3) than in post-MI men (20.3). This score was also higher in the post-MI population than in the general working population, both for women (30.3 compared with 17.0) and men (20.3 compared with 14.1). Psychologic distress was more prevalent in post-MI women than in post-MI men (prevalence ratio [PR], 1.62; confidence interval [CI], 1.27–2.07). This score was also higher in post-MI women and post-MI men than in the general working population (PR, 2.18; CI, 1.75–2.71 and 1.76; CI, 1.48–2.08, respectively).
Conclusions: Among the presumably fittest post-MI patients, namely those who had returned to work, psychologic distress was significantly more prevalent than in the general working population, particularly among women. Further research is needed to shed light on prognosis in post-MI workers experiencing psychologic distress and on adequate intervention before and after their return to work.
Key Words: psychologic distress • post-MI patients • return to work
Abbreviations: PR = prevalence ratio; CI = confidence interval; MI = myocardial infarction; PSI = Psychiatric Symptom Index.
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INTRODUCTION
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Thereis convincing evidence that psychologic factors contribute to the pathogenesis (1–3) and recurrence of coronary heart disease (CHD) (4–8). Depression, as well as symptoms of anxiety and depression, have been identified as independent risk factors for 6-month (9,10), 1-year (4), and 5-year mortality (11) after a myocardial infarction (MI).
Overall, an estimated 20% to 50% of patients have high levels of psychologic distress after an MI, and this prevalence often decreases in subsequent months (12,13). However, little is known about the extent to which post-MI patients who return to work, presumably the fittest post-MI patients, may still experience high levels of psychologic distress compared with other workers. Although an investigation concerning symptoms of psychologic distress, and in particular depression, is recommended as part of the management of an MI, no such evaluation is recommended before a return to work (12). Despite its high prevalence and the increased risk it poses for subsequent cardiovascular disease (6–8), depression remains underdiagnosed and thus undertreated (6).
The objectives of the present study were to assess the prevalence of psychologic distress in men and women returning to work after a first, recent MI and to compare this prevalence with the prevalence observed among men and women of the general working population.
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METHOD
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Postmyocardial Infarction Workers
Data on post-MI workers were collected in the context of a prospective cohort study designed to evaluate the effect of the psychosocial work environment on the prognosis after a first MI (14). Between October 1995 and November 1997, study participants were recruited in 30 hospitals throughout the province of Québec, Canada. Recruitment was conducted among 60-year-old or younger patients admitted to hospital for a first MI. Eligible subjects were those who had been holding a paid job in the 12 months before admission, had returned to work within 12 months after their first MI, and worked at least 10 hours per week at the time of the interview (N = 1215). All subjects provided signed, informed consent for study participation before being discharged from the hospital. A telephone interview was conducted with each subject within 4 weeks (±1 week) after their return to work. The mean length of time between the MI and return to work was 3.8 months for women and 3.5 months for men (p = .30). The study population was composed of 990 individuals (106 women and 884 men), ie, 82% of the 1215 eligible patients.
General Population Sample
The reference population was comprised of participants in the 1998 Québec Social and Health Survey. These participants (70% of the randomly selected individuals from the Quebec Health Insurance register) constitute a representative sample of Québec’s general population (15). Among the 9251 workers 25 to 59 years old, individuals who worked fewer than 15 hours per week at the time of the interview (n = 199) or with missing data on this variable (n = 120) were excluded. The 15-hour criterion was chosen according to the categories available in the survey. In addition, 154 people with missing data on psychologic distress were excluded. Thus, the reference population totaled 8829 individuals (3823 women and 5006 men).
Psychologic Distress
Psychologic distress was measured in both populations with the 14-item validated French version of the Psychiatric Symptom Index (PSI-14) (16), initially developed by Ilfeld (17). This instrument measures the presence and intensity of symptoms of depression (six items), anxiety (four items), cognitive disturbances (two items), and anger (two items) in the week preceding the interview. PSI-14 was administered through a telephone interview among post-MI workers and through a self-report questionnaire among participants of the general population sample. The full 29-item version of the PSI has been shown to measure seven of nine criterion-based symptoms of Major Depressive Episode and five of eight criterion-based symptoms of Generalized Anxiety Disorder (18) as defined in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV). The high concordance between the PSI-29 and the PSI-14 in the validity study (16) makes it highly plausible that such an association with DSM-IV symptoms also exists for the PSI-14. In addition, the PSI-14 has good concomitant validity with regard to four other measures of mental health, namely consulting a health professional for a mental health problem, being hospitalized for this type of problem, the presence of suicidal ideas or attempts at suicide, and the consumption of psychotropic medication (16). A total score of psychologic distress and scores on each subscale were calculated with a range of 0 to 100 from the answers to the 14 items of the PSI. Individuals with scores 
26.19 on psychologic distress, which represents the highest quintile observed in the general population (women and men combined) seen in the 1992 to 1993 Québec Social and Health Survey (19), were considered as prevalent cases of psychologic distress.
Analysis
The study and reference populations were compared as a function of several characteristics using chi-squared tests. Mean PSI scores were calculated and compared between women and men in the post-MI population, as well as between the post-MI and general population, by using the Student t and Wilcoxon tests (20). Weighting factors were applied to the data from the reference population, as recommended by the Québec Health Survey (19). The mean PSI score was first adjusted individually for each sociodemographic variable (age, civil status, education, and perceived economic situation) and then simultaneously for all variables using a covariance analysis (21). Next, prevalence of psychologic distress and prevalence ratios (PR) for psychologic distress and their 95% confidence intervals (CI) (22) were calculated for women and men in both populations. Prevalence and PR were adjusted individually for each sociodemographic variable and simultaneously for all variables using log-binomial models (23). The adjustment effect was chiefly generated by age, entered as a categorical variable (seven categories of 5-year-intervals: 25–29 years, 30–35 years, and so on). For all analyses, potential confounding variables (except age) were categorized as presented inTable 1. The linearity of the relationship between age and prevalence of psychologic distress was verified graphically and with polynomial regression (22).
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TABLE 1. Distribution of Sociodemographic Characteristics Among a Post-Myocardial Infarction (MI) Working Population and the General Working Population (GWP)
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RESULTS
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Among the post-MI working population and among the general working population, more women than men were divorced, separated, or widowed (Table 1). Less women than men in the post-MI population had a university degree. Comparisons between post-MI workers and the general working population showed that post-MI workers were older and less educated than workers from the general working population (for both women and men). More post-MI workers were divorced, separated, or widowed than in the general population, but less men in the post-MI population had a poor perceived economic situation as compared with men from the general working population.
In the post-MI population, the adjusted mean PSI score was higher in women (30.3) than in men (20.3) (Figure 1). This score was also higher in the post-MI population than in the general population for both women (30.3 compared with 17.0) and men (20.3 compared with 14.1) (Figure 1).
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Figure 1. Adjusted* mean Psychiatric Symptom Index scores in the postmyocardial infarction population and the general working population (GWP).
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These differences were also generally observed for the PSI subscales. Among the post-MI population, means of depressive symptoms were 32.9 for women and 19.9 for men. Among the general population, these means were, respectively, 15.9 and 12.1. Means of anger were 23.9 among women and 16.7 among men in the post-MI population and 17.6 and 14.6 in the general population. For anxiety, means in the post-MI population were 45.6 for women and 32.6 for men, and 26.6 and 23.1, respectively, in the general population. Finally, means of cognitive disturbances were 19.5 among women and 14.1 among men in the post-MI population, and 11.2 and 10.1 in the general workers population. The results of the anxiety and cognitive disturbances subscales should, however, be interpreted with caution as a result of the small number of items composing these subscales (two items each) (16,24).
The adjusted prevalence of psychologic distress was 51.0% in post-MI women and 31.4% in post-MI men who returned to work, as compared with 23.4% in women and 17.9% in men from the general population (Figure 2).
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Figure 2. Adjusted* prevalence of psychologic distress in the postmyocardial infarction population and the general working population (GWP).
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The adjusted PR indicates that psychologic distress was more prevalent in post-MI women than in post-MI men (PR, 1.62; 95% CI, 1.27–2.07) and more prevalent in post-MI women than in women from the general population (PR, 2.18; 95% CI, 1.75–2.71). Psychologic distress was also more prevalent in post-MI men than in men from the general working population (PR, 1.76; 95% CI, 1.48–2.08) (Table 2).
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TABLE 2. Prevalence Ratios and Confidence Interval of Psychologic Distress (PD) in the Postmyocardial Infarction (MI) Population and the General Working Population (GWP)
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DISCUSSION
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The present study’s strengths stem from its extensive population of post-MI individuals, who were recruited from 30 hospitals that were located in both urban centers (two) and smaller communities. This fact ensures the representation of a large range of patient characteristics. The reference population involved a large sample of men and women from Québec’s general working population. Psychologic distress was measured with the same validated instrument in both populations (17) and determined using the same thresholds. Both populations were evaluated in proximate years, thereby excluding period bias. Adjustment was made for age (using fine categories) as well as for marital status, education, and perception of economic situation, therefore ensuring that differences observed cannot be explained by these factors.
In the present study, mean PSI scores were higher and psychologic distress more prevalent in post-MI individuals than in the general working population. Approximately half of women (51.0%) and one third of men (31.4%) who returned to work after an MI presented a high level of psychologic distress, which is roughly twice that observed in workers of comparable age, education, civil status, and socioeconomic situation. This result is found among post-MI individuals who are purportedly in reasonable physical condition and assumed capable of returning to work (12). As previously mentioned, a psychologic health evaluation is recommended before being discharged from the hospital after an MI, but not deemed necessary before a return to work (12). The results of the study show that the psychologic health of post-MI workers remains significantly below levels observed in other workers. Given the significant proportion of paid jobs (20% or more) that involve strong psychosocial stressors (28–29), which have also been shown to generate psychologic distress (30), post-MI workers with a psychologic distress level and who also face strong psychosocial stressors at work may be particularly at risk.
An important gender gap was observed in the present study. A similar gender gap in the prevalence of psychologic distress was observed in a previous study of post-MI patients (4), which may be explained by several factors. First, women may be more inclined to report psychologic difficulties than men (31) and to have a different self-perception of their health. In addition, women appear to undergo a different diagnostic and a less aggressive management approach to coronary disease than men (32–34). According to a quality-of-life study conducted 1 year after congestive heart failure, women perceived less improvement than men (35). Although the effect of these differences on psychologic distress levels is unknown, Frasure-Smith (4) has pointed out that the reasons for the gender gap in the psychologic health of post-MI patients remain controversial and warrant future inquiry. Other factors such as marital dissatisfaction (36) or lack of social integration (36–37), which predicted recurrent cardiac events in the Stockholm Female Coronary Risk Study, might also explain this gap. In terms of post-MI workers, other factors may be at play. Indeed, several studies have reported that women are more exposed to psychosocial factors at work than men (29). Moreover, women often shoulder the double burden of work and family responsibilities (29), which may render them more vulnerable to psychologic difficulties than men. Lastly, hospital admissions for acute MI are much higher in men than in women for all age groups, including those 60 and under (38). Therefore, when such an event does occur in younger women, it may increase the degree of worry about her capacity to perform physically or psychologically under pressure in the working environment. This, in turn, may potentially increase psychologic distress.
One potential limitation of the study is the fact that post-MI workers were interviewed by telephone, whereas the general population completed a self-administered questionnaire. It has been shown that overall levels of several morbidity parameters reported in mail questionnaires tend to be higher than those reported in telephone interviews (25–26). Thus, this limitation may result in an underestimation of the true difference between mean scores and of the true PR comparing post-MI workers with other working individuals. In the present study, a single cutoff point was chosen for both men and women because it provides a common basis for comparing the prevalence of psychologic distress between men and women in the post-MI and general working populations. When gender specific cutpoints (27) were used in the present study, the observed PR comparing post-MI participants with individuals in the general working population (data not shown) remained similar. Therefore, the single cutoff point did not bias our results. Finally, a complementary analysis confirmed that the length of time elapsed between the occurrence of MI and return to work did not modify the results (data not shown).
Previous research has shown greater improvement in mental health for post-MI patients returning to work than for those who had not returned (39). However, this study showed that among the presumably fittest post-MI patients, namely those who had returned to work, psychologic distress was significantly more prevalent than in the general working population, particularly among women. Psychologic distress increases the risk of recurrence and mortality. It also has a significant negative impact on the well-being of both post-MI patients and their family members. Further research is needed to shed light on prognosis in post-MI workers experiencing psychologic distress and on adequate intervention before and after their return to work.
The authors thank the patients and healthcare centers who participated in this study. They also thank Brigitte Larocque and Viviane Cantin who made helpful contributions to the manuscript.
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NOTES
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Received for publication January 14, 2004; revision received July 19, 2004.
Funding for this work was provided by the Fonds de la Recherche en Santé du Québec (FRSQ) and the Heart and Stroke Foundation of Québec. C. Brisson and E. Maunsell are Canadian Institutes of Health Research (CIHR) Investigators. Renée Bourbonnais holds a Research Investigator Award from the FRSQ.
DOI:10.1097/01.psy.0000146293.10746.f3
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ABSTRACT
INTRODUCTION
