Our large, retrospective study of the prevalence of cardiometabolic disease as well as all-cause and cause-specific mortality rates among patients diagnosed with schizophrenia relative to a matched comparison cohort revealed unexpectedly small overall differences across the cohorts in morbidity and mortality. While there were significantly higher annual mortality rates in the schizophrenia group the overall mortality-gap with comparison group was not as large as reported in the literature. The difference in the all-cause mortality rates of the two cohorts over the 8-year observation period appears predominantly attributable to mortality from atherosclerosis/HTN, suicide, and other causes that are consistently more common among the schizophrenia patients compared to the comparison population.
We find an overall increase in cardiometabolic disease for both the schizophrenia and the comparison populations. This is likely due to many factors including intensified screening and lower diagnostic thresholds (for T2DM for example). The observed increasing prevalence of obesity mirrors that of the general U.S. population and likely explains at least some of the rise in prevalence of other morbidities for which obesity is an important risk factor [30
]. For some cardiometabolic conditions, prevalence was lower in the schizophrenia group than the comparison group despite substantially higher rates of tobacco exposure, comparable rates of obesity, and the added cardiometabolic risk associated with some second generation antipsychotics. This may result from lower levels of diagnostic testing in this population, due in part to the clinical demands of managing mental illness. Although schizophrenia patients had higher rates of health care encounters (psychiatric and non-psychiatric) compared to the non-SMI group, these encounters may focus on acute conditions or consequences of mental illness rather than screening and prevention which may explain some differences in documented disease prevalence [32
]. While lower rates of testing may explain relative low prevalence of some diseases in the schizophrenia population, the modest differences in cardiometabolic mortality suggest that disease prevalence in the two populations is not dramatically different [34
Rates of much morbidity in the schizophrenia group are comparable with non-SMI Veteran population, yet for both groups, rates were significantly greater than the general U.S. population. For example, the prevalence of diabetes and obesity (BMI≥30) in 2005 for men between the ages of 40–59 years old averaged 7.9% and 39.7% respectively in objectively measured samples of American adults [35
], whereas the concurrent rates in the cohort of non-SMI Veterans averaged 24.1% and 40.7% and 24.9% and 40.6% in the schizophrenia group. VHA FY 2010 operational data indicate that the combined prevalence of overweight/obesity is 77% among VA patients (39% for obesity only), 10% greater than the general U.S. population [37
]. These figures underscore the morbidity burden in the VA patient population that distinguishes it from general U.S. population and validate our choice of Veterans without SMI as the best comparison population.
Mortality is a critical measure of effectiveness of specific clinical treatment strategies [2
]. Our findings support conclusions of a 2009 publication reporting a 1.5-year difference in life expectancy among the general population of VA patients with and without SMI [38
]. Likewise, a 2010 survey-based publication [39
] comparing the mortality for VA patients with and without schizophrenia found that the hazards ratio for death for Veterans with schizophrenia compared to those with no mental illness was 1.2, significantly lower than the average 2.5 mortality ratio reported in community samples [3
]. The similar rates in mortality among Veterans with and without SMI treated through VA healthcare facilities contrasts reports of a life expectancy gap of over 20–30 years among persons with schizophrenia compared to the general population even in settings with socialized medicine including the Nordic countries and Taiwan [6
]. Gaps in mortality of this magnitude among people with serious mental illnesses have also been observed in the U.S. and in other countries [1
While not the primary focus of the current study, mortality rates for cancer and suicide were notably lower than reported in other studies [2
]. A number of methodological issues can obscure clear comparisons between the causes of mortality from suicide or specific cancers including the age of the cohort, the length and decade of follow-up, the cohort size, patient access to quality integrated and preventive health care services, and the reliability of data to measure causes of death. However, crude and unadjusted mortality findings from the current study are consistent with results from a recent retrospective study [41
] examining causes of death and years of potential life lost (YPLL) among decedents with a serious mental illness persons from the general population in a Midwestern U.S. state. Researchers found that heart disease was the leading cause of death in both groups while cancer was the second leading cause of death in the general population but only the fifth cause of death for SMI patients (suicide was not in the top 10 causes of death for SMI patients overall). However, suicide, accidents, and cancer were leading causes of premature mortality (YPLL), causing the authors to conclude that community mental health clinics should place more emphasis on integrated care and preventive screening for these risks. In addition, mortality and morbidity results from the current study not only parallel similar findings reported by Bouza and colleagues in Spain [42
], but also the leading cause of death (CVD) and mortality gap (i.e., 8 years) in a community-based study of American patients with mental disorders published by Druss et al. [43
Indeed the relatively small disparities observed for patients within
VA may be due to the unique, nationally and regionally integrated nature of this system. The VA's nationally integrated health care system is unique compared to other national health systems because of the high-risk population that the VA serves. Unlike many health systems, patients not only have access to mental and physical health care, but also receive targeted services to screen for and prevent both suicide and many forms of common cancers that might be attributed to exposures incurred during military service. The VA has made integrated care a priority for patients with psychotic disorders since landmark studies were published in 2001 suggesting this approach improves outcomes [33
]. Patients with schizophrenia have greater access to substance abuse treatment services [45
], inpatient and intensive case management to facilitate recovery, and immediate access to primary care in the same facility. As one of the largest single providers of mental health care in the U.S., the VA has also been at the forefront in implementing mental health parity, notably through the Mental Health Strategic Plan and the Uniform Mental Health Services Handbook. We speculate that lower unadjusted prevalence rates for cancer and suicide most likely reflect significant efforts to enact quality improvement efforts to target these risks for VA patients in general. Not only are older Veterans more likely to receive preventive screening for conditions like cancer than similar individuals outside the VA [46
], but patients who often do not receive preventive screenings in community settings due to conditions like obesity are actually more likely to be screening in the VA [48
]. Finally, while quality improvement initiatives such as the implementation of a national electronic medical records system has radically improved care for all Veterans [24
], efforts to improve coordination of care between specialty mental health and medical health providers is an ongoing process.
Present findings do not adjust for the prevalence of common psychiatric comorbidities that may raise CVD risk such as anxiety or depressive disorders. However, in a 9-year retrospective cohort study of 559,985 VA patients that examined the effects of mental health diagnoses on all-cause mortality, Chwastiak and colleagues [39
] reported that only VA patients with schizophrenia and substance abuse disorders had an increased risk for all-cause mortality, even after adjustment for psychiatric
and medical comorbidity, obesity, current smoking, and exercise frequency. While Chwastiak et al. did not address CVD mortality specifically, Kilbourne and colleagues [49
] conducted a similar 8-year retrospective study of 147,193 VA patients with and without mental disorders, and found that VA patients with schizophrenia or other psychotic disorders, were more likely to die from heart disease-related mortality than Veterans diagnosed with depression or bipolar disorder, even after adjusting for sociodemographic factors, co-occurring diagnoses, and behavioral variables, including smoking and physical inactivity. These two studies offer support to the validity of the current study's findings despite limitations raised by analyses unadjusted for covariates. Subsequent studies will report the influence of important confounding variables including, exposure to specific psychiatric medications suggested to affect the onset and progression of CVD (e.g., antipsychotic medications).
Our finding of a mortality gap much smaller than that reported by other studies may also result from our choice of matched Veterans as our comparison population. We believe the relative homogeneity of U.S. Veterans making up both our schizophrenia and non-SMI groups, permits us to isolate more than other researchers to date, the impact of schizophrenia on mortality, at least for schizophrenia patients similar to our cohort. Other explanations for the small mortality gap we observed include possible selection effects. VA SMI patients are often diagnosed after enlistment and during military service, and may have had higher premorbid functioning compared to the general U.S. population with schizophrenia prior to their first psychotic episode. Additionally, early diagnosis and access to appropriate and continuous mental health care may help to mitigate the pathophysiological effects of psychosis on disease risk factors and help to identify common and avoidable medical conditions that can contribute to premature mortality if untreated (e.g., infectious disease, lung disease).
Perhaps most importantly, we note morbidity and mortality among Veterans with and without schizophrenia did not improved appreciably in the 8 years studied. This suggests, like the general U.S. population additional efforts are needed to improve the health of Veterans.