Department of Public Health, The University of Western Australia, Perth, Western Australia
Department of Psychiatry and Behavioural Science, The University of Western Australia, Perth, Western Australia
Department of Public Health, The University of Western Australia, Perth, Western Australia
Correspondence: David Lawrence, Centre for Developmental Health, Curtin University of Technology, Telethon Institute for Child Health Research, PO Box 855, West Perth WA 6872, Australia. Tel: +61 8 9489 7720; fax: +61 8 9489 7700; e-mail: dlawrence{at}ichr.uwa.edu.au
Declaration of interest None. Study funded by National Health and Medical Research Council of Australia. Setting up of Western Australian (WA) Health Services Research Linked Database funded by Lotteries Commission.
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ABSTRACT |
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Aims To investigate the association between mental illness and ischaemic heart disease (IHD) hospital admissions, revascularisation procedures and deaths.
Method A population-based record-linkage study of 210 129 users of mental health services in Western Australia during 1980-1998. IHD mortality rates, hospital admission rates and rates of revascularisation procedures were compared with those of the general population.
Results IHD (not suicide) was the major cause of excess mortality in psychiatric patients. In contrast to the rate in the general population, the IHS mortality rate in psychiatric patients did not diminish over time. There was little difference in hospital admission rates for IHD between psychiatric patients and the general community, but much lower rates of revascularisation procedures with psychiatric patients, particularly in people with psychoses.
Conclusions People with mental illness do not receive an equitable level of intervention for IHD. More attention to their general medical care is needed.
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INTRODUCTION |
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METHOD |
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Classification of mental disorders
Principal psychiatric diagnoses were assigned from the records of contacts
with mental health services. The Mental Health Information System (MHIS) is a
core component of the WA Linked Database. The MHIS records separate diagnoses
for each contact with mental health services using ICD9. The final
diagnosis was extracted for each episode of care. The latest informative
psychiatric diagnosis across the episodes was then assigned as the principal
psychiatric diagnosis for each patient according to the following hierarchy of
diagnoses:
For instance, if the last episode of care recorded a diagnosis of alcohol dependence, but the previous episode recorded schizophrenia, then a diagnosis of schizophrenia was assigned. The purpose of this strategy was to give precedence to the more severe disorders, and to allow for certain conditions such as alcohol or drug dependence to be considered as a potential comorbidity of a psychotic condition. More than 70% of people on the MHIS had only one diagnosis recorded (at the level used in this study). Of the remaining cases there were three main groups: those who had a less-specific diagnosis (such as depressive disorder not elsewhere classified) together with a more-specific diagnosis (such as neurotic depression); those who had an alcohol/drug condition as well as a psychotic condition; and those for whom the specific type of psychosis had been refined after further observation (particularly between schizophrenia and affective psychosis). The hierarchical approach was designed to select the most appropriate diagnosis in these cases.
Statistical methods
Age-standardised rates of mortality from IHD were calculated for the
general population, and for people who had contact with mental health
services. Direct standardisation was used
(Rothman, 1986), with the
Western Australian population used as the standard
(Australian Bureau of Statistics,
1980-1998). For population rates, the denominators were calculated
from estimated resident population figures published by the Australian Bureau
of Statistics (Australian Bureau of
Statistics, 1980-1998). Among users of mental health services,
calculation of mortality rates was restricted to 165 699 patients whose first
contact with mental health services occurred during 1980-1998, excluding 44
430 patients with previous contact. This was done to avoid the results being
biased by the healthy-survivor effect. The start of follow-up was the date of
each patient's first contact with mental health services. They were then
censored either at death or on 31 December 1998. Rates were calculated by
principal psychiatric diagnosis and gender. Rates were also calculated
separately for each year in the study period. Rate ratios were calculated
comparing the cohort of users of mental health services with the entire
Western Australian population. For each rate and rate ratio, 95% confidence
intervals were calculated.
Rates of first hospital admission and rates of vascularisation procedures were calculated in a similar fashion. The only difference was that the full cohort of 210 129 patients was used, as there was no evidence of a healthy-survivor bias. Rates were also calculated restricted to the inception cohort but, as there was no evidence of any differences, results shown here are from the analysis of the full cohort (which has greater statistical power). Rates were restricted to the first admission for each patient during 1980-1998, and follow-up began on 1 January 1980 for patients whose first contact with mental health services occurred before 1980. When examining individual heart conditions and procedures, calculations were made separately for each condition and individual patients could contribute to more than one condition if they had separate admissions for separate conditions. Patients were censored at time of admission or procedure, or on 31 December 1998.
Poisson regression was used to analyse trends in IHD mortality. Poisson regression models the relationship between counts of events (in this case, deaths) and a set of explanatory variables (in this case, age and year). Separate models were run for each gender for both the cohort of users of mental health services and the total Western Australian population.
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RESULTS |
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There has been a steady decline in the mortality rate due to IHD in the Western Australian population overall during 1980-1998, dropping from 209 per 100 000 person-years to 143 per 100 000 person-years in males, and from 139 per 100 000 person-years to 117 per 100 000 person-years in females. In contrast, the IHD mortality rate over the period has remained approximately constant in male psychiatric patients (an average 280 per 100 000 person-years) but increased from 153 per 100 000 person-years to 234 per 100 000 person-years in female psychiatric patients (Fig. 1).
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Poisson regression analysis of the mortality rates found that, in the Western Australian population, the mortality rate had been decreasing by 1.9% per year (95% CI 1.7-2.1%) in males and by 0.7% per year in females (95% CI 0.5-1.0%). In contrast, in users of mental health services the mortality rate was not significantly changed in males (95% CI for annual increase -0.5% to 0.9%), and was increasing at a rate of 2.2% per year in females (95% CI 1.5-3.0%).
Whereas psychiatric patients had higher mortality rates, the age-standardised rates of first hospital admission of psychiatric patients for IHD were little different from those in the general population (Table 2). The number of first hospital admissions for acute myocardial infarction was close to that expected for males but lower than expected for females. Rates significantly higher than expected were observed for other acute and subacute IHD, and marginally elevated rates for angina pectoris. The rate of hospital admissions for coronary atherosclerosis was slightly but significantly down in male psychiatric patients, and there was a small but statistically significant elevation in female psychiatric patients.
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Mortality and first hospital admission rates for IHD relative to the general community are shown in Table 3 by principal psychiatric diagnosis. Patients with dementia experienced the highest excess mortality, followed by patients with other psychoses. In males, elevated mortality rates were observed in all diagnostic groups except personality disorders, adjustment disorder and non-specific diagnoses. However, only males with neurotic disorder and attempted self-harm had elevated rates of hospital admission for IHD. Males with schizophrenia were only 60% as likely to be admitted for IHD compared with males in the general population, despite being 1.8 times as likely to die from IHD. A similar pattern of excess mortality was observed in females, with the exception of females with schizophrenia. For patients with neurotic disorders, significantly elevated hospital admission rates were observed, together with correspondingly elevated mortality rates. For most other conditions, including dementia, alcohol and drug disorders, schizophrenia and other psychoses, personality disorders and depressive disorder, the mortality rate ratio was markedly higher than the hospital admission rate ratio.
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Of IHD deaths, 13% occurred within 28 days of admission for acute myocardial infarction. The 28-day case fatality rate was directly comparable between people with previous contact with mental health services (12.2% mortality) and the remainder of the population (13.0% mortality). The excess mortality from IHD in psychiatric patients occurred outside the hospital environment. In those who survived for at least 28 days following admission for acute myocardial infarction, longer-term survival was worse in psychiatric patients (12% mortality after 2 years, compared with 7% mortality in the remainder of the population).
During 1980-1998, there were 30 593 hospital admissions for revascularisation procedures (17 348 for coronary artery bypass grafts and 13 245 for removal of coronary artery obstructions), representing 23 900 individual patients. Of these patients, 1807 had previous contact with mental health services. First hospital admission rates for revascularisation procedures were lower than expected in male psychiatric patients, and about what was expected in females (Table 4). Slightly lower rate ratios were observed for coronary artery bypass grafts compared with removal of coronary artery obstructions. Procedure rates were significantly lower in males with dementia, alcohol/drug disorders, schizophrenia, affective disorder and other psychosis, and in females with schizophrenia. Patients with neurotic disorders had elevated rates of revascularisation procedures.
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DISCUSSION |
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Risk factors for cardiovascular disease
Risk factors for cardiovascular disease include family history, smoking,
poor diet, high cholesterol, obesity, lack of exercise and stress levels. The
1997 National Survey of Mental Health and Wellbeing found that 43% of Western
Australians with a diagnosable mental health condition were current smokers,
compared with 24% among people without a mental disorder
(Australian Bureau of Statistics,
1999). The prevalence of smoking was even higher among patients
with psychosis, at 66% (Jablensky et
al, 1999). Obesity is known to be a problem among people with
chronic mental illness (Wallace &
Tenant, 1998) and has been linked to overeating, underactivity and
ignorance of correct dietary principles
(Gopalaswamy & Morgan,
1985; McCreadie et
al, 1998). Weight gain is also a known side-effect of some
antipsychotic medications (Silverstone
et al, 1988; Allison
et al, 1999). Lower levels of physical fitness have also
been found in mental illness, linked to physical inactivity
(Martinsen, 1990).
Trends in cardiovascular mortality
The rates of cardiovascular mortality in the general population of Western
Australia have been in steady decline over the period from 1980 to 1998.
Whereas public health campaigns and the introduction of new therapies have
been shown to be very successful in the general population, it would appear
that people with mental illness have received little or no benefit from this
progress. Over the same period, cardiovascular mortality rates have increased
in women known to mental health services and have remained approximately
constant in men. The evidence cited above concerning cardiovascular risk
factors in mental illness suggests that health campaigns targeted at these
risk factors have had no impact in this population. Users of mental health
services are a significant group numerically, representing 8% of the adult
population of Western Australia. Therefore, public health and clinical
strategies specifically targeted towards this group should be developed.
Psychiatric patients had a higher death rate from acute myocardial infarction than did the general community, although the rate of hospital admission was no higher than expected in males and marginally lower than expected in females. Outcomes following acute myocardial infarction are affected by how quickly emergency treatment can be administered. The lower rates of hospital admission could be due to the fact that psychiatric patients with acute myocardial infarction died before they could be admitted to a hospital emergency department. It is possible that some psychiatric conditions, such as schizophrenia, may interfere with effective communication of symptoms. In critical conditions such as acute myocardial infarction, this may result in a delay of treatment that contributes to excess mortality. Social isolation could also be an issue, as people with chronic mental disorders are more likely to live alone, in a hostel or even to be homeless. Consequently, they are more likely to be alone at the time of an infarction and therefore to lack assistance.
There are other factors that may contribute to a high rate of coronary events in this group of patients. People with mental illness may experience an elevated risk of acute coronary events due to causes of fatal arrhythmias such as heavy smoking and possibly certain psychopharmacological agents (Glassman, 1998; Appleby et al, 2000). Considering the tentative evidence that antipsychotic polypharmacy may be associated with reduced survival (Waddington et al, 1998), there is a need for further research into the cardiotoxic effects of pharmacotherapy in psychiatry.
Mental illness and general health care
Although hospital admission rates for some ischaemic heart conditions were
mildly elevated in users of mental health services compared with general
population rates, the excess of mortality was considerably higher than the
excess of hospital admission. This raises the question of whether, in spite of
their rate of hospital admission, psychiatric patients are actually receiving
the same level of care, relative to clinical need, that is afforded the
general community for circulatory system disorders. Rates of revascularisation
procedures were low considering the high rate of mortality. The results imply
that people with mental illness are not receiving these interventions at a
level matching that in the general population.
Druss et al (2000) found lower rates of cardiovascular procedures undertaken in an index admission for acute myocardial infarction if the patient had a mental disorder recorded as a comorbidity. Our results confirm in a large population-based record-linkage study that the total cardiovascular procedure rate in users of mental health services is very low relative to their heavy burden of cardiovascular morbidity and mortality, although this varies by diagnosis.
When examining procedure rates by diagnosis, it is clear that patients with schizophrenia have a much lower rate of cardiovascular procedures, even though these patients have among the highest levels of smoking, obesity and other cardiovascular risk factors. Is it possible that circulatory system disorders are underdiagnosed in mental illness, contributing to the large excess in mortality? There is some indirect evidence to support this conjecture. It is known that mental health services can miss physical conditions in their patients (Koranyi, 1979; Koran et al, 1989), and that not all psychiatrists undertake physical examinations of their patients (McIntyre & Romano, 1977; Patterson, 1978). Moreover, Kendrick (1996) reported that in a survey of general practices he found that cardiovascular risk factors were regularly recorded in the notes for adults with long-term mental illness, but that the general practitioners had rarely attempted to intervene.
Stigma
Patients with neurotic disorders have a higher than average rate of
revascularisation procedures, possibly because they comprise a subset of
individuals with anxiety or somatisation disorders who are more likely to seek
specialist consultation, or because the pressure of the physical symptoms of
heart disease may be more difficult for individuals whose mechanisms of coping
with stress are already challenged. In contrast, patients with schizophrenia
are clearly disadvantaged regarding access to such treatment. These findings
concerning the standard of health care provided to people with mental illness
raise the question of whether the stigma associated with mental illness
extends beyond the general community into the medical profession. Although
implicit stigmatising attitudes on the part of providers of specialist care
may play a role (Haghighat,
2001), the disparity in service provision may also be due to
socio-economic factors. The majority of revascularisation procedures are
performed as elective interventions to which carriers of private health
insurance have readier access than people covered only by Medicare (the
Australian national health service). Considering that, in Australia, only 13%
of people with psychotic disorders have private health insurance, as compared
with an average of 32% for the general population
(Jablensky et al,
1999), the compound predicament of this group of psychiatric
patients deserves further study, to develop health care policy and
interventions to reduce these inequalities.
Given that the excess risk of heart disease rather than the excess risk of suicide is the leading killer of people with mental illness, mental health services should adopt a more proactive role in identifying patients with cardiovascular problems and referring them for early intervention. People with mental illness may benefit also if general practitioners have a greater role in their primary medical care.
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Clinical Implications and Limitations |
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LIMITATIONS
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Received for publication February 15, 2002. Revision received June 24, 2002. Accepted for publication September 4, 2002.
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