Although several studies have found evidence that major depression is associated with increased risk of early mortality from general medical illnesses, fewer studies have investigated premature mortality from such illnesses among individuals with bipolar disorder (
1 ). In the past, excess deaths associated with bipolar illness were attributed mostly to unnatural causes, such as suicide, homicide, and accidents (
2,
3,
4,
5 ). Over the past decade, there is increasing evidence that patients with bipolar illness may be at higher risk of premature death from general medical disorders.
Emerging data indicate that although standardized mortality ratios are higher for unnatural causes (that is, suicide and accidents), the majority of excess deaths among persons with bipolar disorder are secondary to comorbid general medical conditions. The causes of this excess mortality may include unhealthy diet (
6 ), obesity (
6,
7 ), binge eating (
8,
9 ), sedentary lifestyle (
6,
10 ), smoking (
11,
12,
13 ), social deprivation (
14,
15 ), living alone or being homeless or single (
15,
16 ), poor access to and less effective use of health services (
17,
18,
19,
20,
21 ), biased attitudes among health care providers (
18,
22,
23,
24,
25,
26,
27,
28,
29,
30 ), failure of psychiatric providers to ask about or address medical problems (
31,
32,
33 ), the "competing needs theory" (that is, health care providers might give precedence to conditions that need immediate attention while management of other conditions is delayed or forgotten) (
34,
35,
36 ), and comorbid substance use disorders (
37,
38,
39,
40 ). Biologic factors associated with bipolar illness, such as stress-related effects on the immune system (
41,
42,
43,
44,
45 ) and on the hypothalamic-pituitary axis (
41,
46,
47 ), increased activity of the sympathetic nervous system (
48,
49 ), and metabolic side effects of pharmacologic treatments, may also increase the risk of mortality (
50,
51,
52,
53,
54,
55 ).
The association of psychopharmacologic agents with obesity and type 2 diabetes has also helped stimulate research about general medical outcomes of patients with severe mental illness. Olanzapine, which was approved in 2000, was the first second-generation antipsychotic to gain approval by the Food and Drug Administration for the treatment of acute mania and subsequently for maintenance treatment. Since then four other second-generation antipsychotics have been introduced and approved for the treatment of bipolar disorder (
56,
57 ). Although second-generation antipsychotics have less risk than first-generation agents of side effects, such as extrapyramidal symptoms, tardive dyskinesia, and hyperprolactinemia, evidence shows that some of these medications are associated with obesity and metabolic abnormalities, which may increase morbidity and mortality resulting from diabetes and vascular disease (
58,
59 ). Many patients with bipolar disorder are treated with mood stabilizers that are also associated with increased risks of obesity and metabolic syndrome.
The aim of this study was to review the literature in regard to excess mortality attributable to medical problems among patients with bipolar spectrum disorders. Verification that bipolar disorder is associated with premature mortality from general medical illnesses could lead to development of health services models that integrate preventive medical interventions into community mental health settings. Given that most of the studies reviewed did not include structured psychiatric interviews, the following diagnoses were included in the definition of bipolar spectrum disorders used in this study: bipolar disorder, schizoaffective disorder, affective psychosis, and affective disorder severe enough to require inpatient admission or treatment with lithium.
Results
Through the electronic and manual searches, we identified 44 English-language articles. A total of 27 were excluded for the following reasons: eight articles reported studies that included fewer than 100 patients, seven articles presented data from studies that included patients with several psychiatric diagnoses (that is, we could not differentiate patients with bipolar spectrum illnesses), five articles reported on samples already included in another paper, five articles reported studies that did not separate suicide and nonsuicide mortality, and two articles reported studies that did not include a comparison group.
Our systematic review of the literature identified 17 studies that met the inclusion criteria.
Tables 1 and
2 divide the studies into more generalizable samples, which we defined as those with more than 2,500 patients with bipolar spectrum illnesses (
Table 1 ) and smaller studies with fewer than 2,500 patients with these illnesses and with samples selected on the basis of lithium use (
Table 3 ).
In one of the larger studies, Laursen and colleagues (
60 ) compared mortality rates among patients with severe mental illness who were admitted to a psychiatric hospital and rates among those without a history of psychiatric hospital admission in the entire adult population of Denmark after controlling for age, gender, and calendar year. Among patients with bipolar or schizoaffective disorder, an inverse relationship was found between age group and mortality rate. Compared with persons without major psychiatric disorders, patients with either bipolar or schizoaffective disorder had significantly higher mortality risk in all age groups, but SMRs were highest in the younger age groups. In addition, SMRs were also higher for all natural causes of death (cardiovascular, respiratory, and endocrine conditions) except for cancer both among patients with bipolar disorder and among those with schizoaffective disorder.
Kisely and colleagues (
61 ) studied mortality rates among patients who had received psychiatric treatment (inpatient and outpatient) in Nova Scotia, Canada, and compared these rates to those in the entire adult Canadian population. Controlling for age and gender, the regression analysis showed that an "affective psychosis" diagnosis was significantly associated with increased mortality risk (SMR=1.35, 95% confidence interval [CI]=1.24–1.47.) Among patients with affective psychosis, mortality risk from natural causes was not increased in most categories except for cerebrovascular disease and pneumonia or influenza.
Lawrence and colleagues (
24 ) studied the rate of hospital admissions, revascularization procedures, and deaths from ischemic heart disease among more than 210,000 patients with mental illness and compared it with the rate in the general population of Western Australia, after adjusting for age and gender. Among patients with affective psychosis, mortality from ischemic heart disease was significantly higher for both sexes, although the hospital admission rate was not different from that in the general community. The rate of revascularization was significantly lower for psychiatric patients. Among users of mental health services, ischemic heart disease was responsible for 16% of excess deaths (foremost cause of excess deaths), compared with 8% of excess deaths caused by suicide.
Osby and colleagues (
62 ) studied mortality rates among more than 15,000 Swedish citizens who had a hospital discharge diagnosis of bipolar disorder and compared it with the mortality rate for the Swedish population. This study controlled for sex, age at admission, and calendar year. Among patients with bipolar disorder, SMRs from all natural causes were significantly higher for both sexes. Cardiovascular disease was the most frequent cause of death. This study showed that except for cancer and central nervous system diseases among males, all other natural causes of death were higher among patients with bipolar disorder.
In another Danish study, Hoyer and colleagues (
63 ) investigated mortality and cause of death among more than 54,000 patients with affective disorder who were admitted to a psychiatric hospital. After the analyses controlled for age, gender, duration of illness since first psychiatric hospitalization, and calendar year, SMRs from all natural causes were higher among patients with affective disorder compared with the general population of Denmark. In the bipolar disorder subgroup, SMRs for natural causes were highest in the first year after admission and decreased as duration of disease increased over the course of years.
The five studies discussed above were categorized as larger studies, that is, more than 2,500 patients. Twelve of the other studies reviewed were categorized as smaller studies with fewer than 2,500 patients (range 100 to 2,168) (
64,
65,
66,
67,
68,
69,
70,
71,
72,
73,
74 ). The smaller studies may have been underpowered to find differences in mortality. Most of these studies compared specific medical causes of death among patients with affective disorders and a control group; only five studies reported SMRs for deaths from all natural causes (
5,
64,
65,
66,
67 ). In a prospective study with an average follow-up period of 19 years, Dutta and colleagues (
65 ) studied causes of death among 235 patients with newly diagnosed bipolar disorder. The study showed no increase in mortality from natural causes compared with the 1991 population of England and Wales, except for deaths from infectious and respiratory diseases among females. In another prospective study, over a 34- to 38-year period, Angst and colleagues (
5 ) showed that SMRs for all natural causes and for cardiovascular disease (but not cerebrovascular disease or cancer) were significantly higher among 220 inpatients with bipolar or schizoaffective disorder compared with the general population of Switzerland.
In a study in Japan, Saku and colleagues (
68 ) found that SMRs among 187 patients with manic-depressive illness were significantly higher for hypertension among females and for pneumonia and bronchitis among males compared with adults in the Japanese population. In a retrospective British follow-up study over 17 years completed by Sharma and Markar (
69 ), the MR from cardiovascular and respiratory disorders was significantly higher among 472 patients with bipolar disorder compared with a control group. In a five-year follow-up study, Zilber and colleagues (
66 ) examined the risk of medical mortality for more than 7,868 person-years (the actual number of patients was not reported) among Israeli patients who had at least one inpatient psychiatric treatment for affective disorder during 1978. After the analyses controlled for age, sex, and ethnicity, the SMR for natural causes among patients with affective disorder was significantly higher than that in the general population of Israel. The higher SMR for these patients was attributable to a higher mortality rate from infectious diseases, whereas the SMR attributable to cardiovascular and cerebrovascular disease together was significantly lower among patients with affective disorder.
Black and colleagues (
67 ) compared mortality among 586 patients who had bipolar disorder with mortality in the general population of Iowa. In a follow-up period of less than two years, SMRs from natural causes were significantly higher among women with bipolar disorder who were depressed and men with bipolar disorder who were experiencing a manic episode. Using data from the Danish Central Psychiatric Register, Weeke and Vaeth (
70 ) identified 417 patients with manic-depression and 1,751 with unipolar depression who had a first psychiatric admission between 1970 and 1972. Compared with the general population, SMRs for cardiovascular disease and cancer were both significantly higher among males, but not among females, with affective disorder. In a 3.5-year follow-up study by Haugland and colleagues (
71 ), the SMR for all causes among 144 patients with affective disorder was significantly higher than the age-specific SMR in New York State. Most deaths were reported to be from heart disease. Tsuang and colleagues (
72 ) studied causes of death among 525 patients with severe mental illness over 30 to 40 years. In the subgroup of 100 patients with mania, the observed to expected mortality ratio for circulatory system diseases among women, but not among men, was significantly higher than in the general population of Iowa over a nine-year follow-up period.
We also reviewed studies with small samples in which patients were selected because they were being treated with lithium. In a Danish prospective study by Brodersen and colleagues (
64 ), 133 patients with affective disorder were started on lithium and followed up for 16 years. Regardless of medication adherence, trends for higher SMRs for all natural causes were found for both sexes, although the all-cause SMR was statistically significant only for female patients. The SMR for cardiovascular disease was not different from that in the general population. Nilsson (
73 ) investigated mortality among 362 patients with a mood disorder or schizoaffective disorder who were treated with lithium for at least one year. Compared with the adult Swedish population, cause-specific SMRs were higher for pneumonia and pulmonary embolism among the patients both when they were taking lithium and when they were not taking lithium. In a Scottish retrospective study by Norton and Whalley (
74 ), 791 patients with affective disorder who had received lithium for at least two months during the ten-year follow-up had a significantly higher SMR for cardiovascular disease compared with the general population of Scotland.