In this retrospective cohort study of a community-based sample of Maryland Medicaid recipients with severe mental illness, we found over 16% of the cohort died within seven years at a mean age of less than 52 years. Compared to the Maryland general population, the standardized mortality ratio was over three and a half times higher in the cohort with severe mental illness, with the main causes of death very similar. Alcohol and substance abuse diagnoses conferred increased risk of death. Mortality rates for those with severe mental illness were elevated particularly in young adults.
Our results are consistent with other studies documenting the overall high mortality rate of populations with chronic mental illness. Mortality rates for heart disease and cancer have been inconsistently elevated in persons with severe mental illness in older studies, although more recent cross-sectional work has shown that these are important causes of death in populations of clients in the public mental health system.(Brown 1997
; Colton and Manderscheid 2006
) A retrospective cohort study from Britain in persons with schizophrenia reported similar relative risks for mortality from heart disease and stroke as our results, but no elevation in mortality for common cancers.(Osborn, et al. 2007
) A recent literature synthesis showed SMRs for heart disease and cancer in schizophrenia comparable to our estimates.(Saha, et al. 2007
Our results underscore the importance of vascular-related disease and cancer in persons with severe mental illness. Heart disease, diabetes mellitus and cerebrovascular disease combined account for one third of all deaths from vascular-related disease and adding cancer increases the proportion to almost half of all deaths due to these causes. A myriad of factors contribute to risk for cardiovascular disease and cancer in persons with severe mental illness. Psychotropic medications contribute to obesity and diabetes, and lifestyle behaviors such as unhealthy diet and smoking increase risk for vascular-related disease and cancers.(Allison, et al. 1999
; Daumit, et al. 2003
; McCreadie 2003
) Poorer quality health care to prevent, detect and appropriately treat these conditions in persons with severe mental illness may also contribute to higher death rates.(Druss, et al. 2000
Although elevated at over three times the SMR of the general population, we found lower standardized mortality ratios for suicide compared to literature syntheses where SMRs for suicide were elevated at 8 to 12 times the general population. Our findings may be explained in part by many published studies using inpatient or clinic-based samples who may be at higher risk for self-harm. (Brown, 1997
; Saha, et.al. 2007
We believe this is one of the first reports to describe mortality rates in persons with severe mental illness stratified by race and gender. While all race and gender groups with severe mental illness had increased SMRs compared to the corresponding Maryland general population categories, the SMR in mental illness was higher for White men than for African-American men and for White women than for African-American women. African American adults in the U.S. population are known to have higher mortality rates than Whites by a factor of up to 1.9.(Jemal, et al. 2008
); in this cohort with severe mental illness, this disparity was substantially narrowed. Possibly, lower socioeconomic status across both Whites and African Americans in this Medicaid population contributed to decreased racial disparity in death rates compared to those seen in the general population. In addition, contrary to general population estimates, within the cohort with severe mental illness, women had higher mortality rates than men. (Minino and Smith et.al., 2001
An important strength of this study is its use of a large cohort of persons with severe mental illness enrolled in Medicaid, not a sample limited to psychiatric hospitals or clinic attendees. We also included age, race and gender in our analyses. The mean age of death in the cohort reflects the relatively young mean age of 41.6 years in the sample. One limitation is that we could not incorporate detailed patient characteristics such as tobacco smoking to assess differences in causes of death.
Another limitation is that while we had a defined cohort by age, enrollment, severe mental illness criteria and geographic region, this sample does not include all persons with severe mental illness in Maryland, and thus may not reflect the mortality experience of all with severe mental illness in the state. We estimate that this cohort represents approximately one third of Maryland Medicaid recipients with severe mental illness, and about 20% of persons with severe mental illness in Maryland. The sample was designed to include persons with severe mental illness using diagnostic and disability criteria. Virtually all in the study cohort (98%) met criteria based on diagnosis and disability. While this analysis compares a Medicaid cohort with severe mental illness to the Maryland general population, we did not have data on a Medicaid population without mental illness, which may be an informative comparison of persons with more similar socioeconomic backgrounds than the general population.
Reliability and validity of demographic variables can be a concern with administrative claims data. However, we found that race and gender were stable in the enrollment files throughout the duration of the cohort. In addition, in interview data from another study using this cohort (Daumit, et.al, 2003
), gender matched Medicaid claims in 99.6% of participants, and race matched in 97.5% of participants.
In conclusion, we found high rates of premature death from preventable medical conditions in a cohort of persons with severe mental illness compared to the Maryland general population. Unlike U.S. mortality rates, in this population with severe mental illness, age-adjusted mortality rates in women were one third higher than in men, and in African Americans were only 10 percent higher than in Whites. Vascular-related diseases and cancer accounted for almost half of all deaths. Further work to understand how to decrease mortality rates in this vulnerable population with severe mental illness is needed urgently.