5 February 2013. Undiagnosed heart disease and cancer steal 12 to 15 years from the lives of people with schizophrenia, reports a study published online January 15 in the American Journal of Psychiatry. Led by Casey Crump of Stanford University, in collaboration with a team from Lund University in Sweden, the study tracked over six million people in Sweden and found that undiagnosed medical conditions—but not unnatural causes of death like suicide—accounted for the shortened lifespans in schizophrenia.
The study suggests that these medical conditions go undetected in people with schizophrenia, even though they tend to have more contacts with the healthcare system. Though antipsychotic drugs themselves were not associated with death (see SRF related news story), the study was unable to say whether the higher rates of smoking by people with schizophrenia were to blame for these.
Premature mortality is a well-known, albeit distressing, finding for people with schizophrenia (see SRF related news story and SRF news story), and narrowing this “mortality gap” means finding its causes. The new study provides one of the most comprehensive surveys of these using Swedish national databases. With data available from both inpatient and outpatient records, the researchers could track diagnoses—whether schizophrenia or other comorbid conditions that didn’t necessarily land someone in the hospital—to obtain a fuller picture of a person’s health.
The study population was all people aged 25 or older living in Sweden, and who had lived there for two or more years, as of January 2003. This amounted to 6,097,834 people, 8,277 of whom were diagnosed with schizophrenia. The researchers followed this cohort for seven years, tracking specific diagnoses recorded in either the Swedish Outpatient Registry or the Swedish Hospital Registry, and deaths recorded in the Swedish Death Registry.
On average, women with schizophrenia died 12 years earlier, and men 15 years earlier, than their counterparts without the disorder. This difference was not accounted for by “unnatural” deaths, meaning suicide or accidents: although unnatural deaths occurred more frequently in schizophrenia, when the subset of people who had died from natural causes was analyzed, the stark gap in mortality remained.
The most common causes of death among people with schizophrenia were ischemic heart disease and cancer. Among all people who died from these conditions, those with schizophrenia were less likely to have received a diagnosis of these conditions. For example, of those people who died from ischemic heart disease, 26.3 percent of people with schizophrenia had been diagnosed with the condition, compared to 43.7 percent of people in the general population. Similarly, of those who died from cancer, 73.9 percent of people with schizophrenia had received that diagnosis, compared to 82.3 percent of those in the general population. This suggested that these conditions went undetected in schizophrenia, since as a whole, the schizophrenia group was seeing doctors, clocking twice as many outpatient clinic visits and hospital admissions per year. Also, when the researchers looked exclusively at those people with schizophrenia who had received a diagnosis of ischemic heart disease or cancer prior to their death, their risk of dying from those conditions fell to general population levels.
Behind the causes
Because smoking is a risk factor for these conditions, it could be that they stem from the prolific smoking habits of people with schizophrenia. The databases, however, did not have information on an individual’s smoking status. To measure what the effect of smoking might be on their risk estimates, the researchers adjusted their calculations by the prevalence of smoking in schizophrenia (70 percent) and the general population (25 percent). This revised their estimates downward, though risk from dying from something like ischemic heart disease was still elevated compared to the general population. This suggests smoking may modulate risk, but information about individual smoking behavior will be needed to better estimate its contribution.
Although the metabolic syndrome induced by second-generation antipsychotic drugs could spur many of these conditions, the study did not find an association between any particular antipsychotic and increased mortality. In fact, not taking antipsychotics increased risk of death from any cause, and aripiprazole and olanzapine use were associated with decreases in risk.
Whether these comorbid conditions reflect something about the cause of schizophrenia, or the consequences of living with it, the study argues that the primary healthcare needs of people with schizophrenia sorely deserve attention.—Michele Solis.
Crump C, Winkleby MA, Sundquist K, Sundquist J. Comorbidities and Mortality in Persons With Schizophrenia: A Swedish National Cohort Study. Am J Psychiatry. 2013 Jan 15. Abstract