AMERICAN JOUENAL OP EPIDEMIOLOGY
Copyright © 1979 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved
Vol. 109, No. 1 Printed in U.SA.
RISK OF SUICIDE AMONG CANCER PATIENTS K. A. LOUHIVUORI AND M. HAKAMA Louhivuori, K. A., and M. Hakama (Finnish Cancer Registry, Lllsankatu 21 B, SF-00170, Helsinki 17, Finland). Risk of suicide among cancer patients. Am J Epidemiol 109:59-65, 1979. Of the 28,857 cancer cases registered by the Finnish Cancer Registry in 1955, 1960 and 1965, 63 patients had committed suicide by the end of 1970. The suicide rate among males was 1.3 times higher (p < 0.01) and among females 1.9 times higher (p < 0.05) than the rate In the general population. The highest suicide risk (relative risk 2.5, p < 0.001) was associated with gastrointestinal cancer. Patients with a non-localized tumor at diagnosis had a two-fold risk of suicide and the rate was higher among patients undergoing no treatment, or treatment with chemotherapy or hormones only. It was estimated that 23% of all suicides among male cancer patients and 46% among female cancer patients was associated with the patients having cancer. neoplasms; suicide
In 1973, the death rate from suicide was in the range 0.1-36.9 per 100,000 person-years in different countries (1). In Finland the rate was 23.5, one of the highest in the world. The risk of suicide is high among males, older age groups and those previously married (2). An increased risk is also found among those with neuropsychiatric diagnoses or serious chronic diseases (3). The purpose of this paper is to evaluate the risk of suicide among cancer patients. In Finland about 12,000 new cases of cancer (6000 males and 6000 females) are diagnosed annually. The leading anatomical sites among males are the lung (one third of all new cases of cancer), stomach (15 per cent) and prostate (8 per cent). The leading sites among females are the
breast (20 per cent), stomach (12 per cent) and uterine cervix (7 per cent) (4). MATERIALS AND METHODS
The series originates from the Finnish Cancer Registry. Every case of cancer diagnosed in Finland has been reported to the Finnish Cancer Registry since 1953. The present series consists of cancer cases diagnosed in 1955, 1960 and 1965, a total of 28,857 cases (14,427 males and 14,430 females). The series was followed up to the end of 1970; by that time, 63 cancer patients had committed suicide. The person-years lived by the 28,857 patients were evaluated according to the age of the patient, calendar period and length of the follow-up period. The expected number of cases was estimated for each age-calendar period group by multiplying the number of person-years by the age- and calendar period-specific death rate from suicide for the total Finnish population. The observed number of deaths was found by identifying all the suicides among cancer patients who died from violent causes. The sex, age, and marital status of the
Received for publication February 21,1978, and in final form June 21, 1978. From the Finnish Cancer Registry, Helsinki, Finland, and the Department of Public Health, University of Tampere, Tampere, Finland. Send requests for reprints to M. Hakama, Professor of Epidemiology, Finnish Cancer Registry, Liisankatu 21 B, SF-00170, Helsinki 17, Finland. Supported in part by Red Feather Fund/The Finnish Foundation for Cancer Research. 59
60
LOUHTVUORI AND HAKAMA
cancer patient, the primary site, extent and treatment of the cancer, and the length of the follow-up were taken as suicide risk factors. The series was classified according to the extent of the disease, into those with a localized cancer, i.e., a tumor with no infiltration into neighboring organs or a tumor which had not metastasized to regional or distant lymph nodes, and those with a non-localized disease. Categories of treatment were surgery, radiation, surgery and radiation combined, other treatment and no known treatment. The primary site of the tumor was classified into the broad categories gastrointestinal, respiratory, genital (including breast), and other anatomical organs. The statistical significance between the observed and the expected number of cases was evaluated using the MantelHaenszel test. Whenever the expected number of cases was less than five, exact Poisson probabilities were computed. The effect of the exposure was
evaluated in terms of relative risk (RR = observed number of cases/expected number of cases), etiologic fraction ((RR - 1)/RR) and population etiologic fraction ((RR - 1)/[RR + (1 - a)/a], where a indicates the prevalence of cancer cases in Finland (5)). The prevalence rates were based on data from the Finnish Cancer Registry (4). RESULTS
By the end of 1970, 63 of the registered cancer patients, 49 males and 14 females, had committed suicide. The observed number of suicides was significantly higher than the expected number, which was 38 for males and 7.5 for females. The excess risk of suicide persisted in almost all age- and sex-specific subgroups (figures 1 and 2). The risk of suicide was increased in categories of marital status enough to allow a meaningful comparison (table 1). The risk of married cancer patients committing suicide was twice that for the normal population. The relative risk for
AGE
FIGURE 1. The observed and expected number of suicides in 1955-1970 among male cancer patients diagnosed in Finland in 1955, 1960 and 1965, by age.
61
RISK OF SUICIDE AMONG CANCER PATIENTS
EXPECTED OBSERVED
AOE
FIGURE 2. The observed and expected number of suicides in 1955-1970 among female cancer patients diagnosed in Finland in 1955, 1960 and 1965, by age. TABLE 1
The observed and expected numbers of suicides in 1955-1970 among cancer patients diagnosed in Finland in 1955, 1960 and 1965, by sex and marital status Women
Men Marital status
Obe.
Exp.
O/E5
Obs.
Exp.
O/E
Unmarried Married Divorced or widowed Unknown
1 33* 8 7
L9 19.7 3.1 13.7
0.5 1.7 2.6 0.5
1 5 7* 1
0.8 2.8 1.2 2.8
1.3 1.8 5.8 0.4
Total
49t
38.0
1.3
14*
7.5
1.9
§ O/E = Observed/Expected (Relative Risk), • p < 0.001.
tp
Copyright © 1979 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved
Vol. 109, No. 1 Printed in U.SA.
RISK OF SUICIDE AMONG CANCER PATIENTS K. A. LOUHIVUORI AND M. HAKAMA Louhivuori, K. A., and M. Hakama (Finnish Cancer Registry, Lllsankatu 21 B, SF-00170, Helsinki 17, Finland). Risk of suicide among cancer patients. Am J Epidemiol 109:59-65, 1979. Of the 28,857 cancer cases registered by the Finnish Cancer Registry in 1955, 1960 and 1965, 63 patients had committed suicide by the end of 1970. The suicide rate among males was 1.3 times higher (p < 0.01) and among females 1.9 times higher (p < 0.05) than the rate In the general population. The highest suicide risk (relative risk 2.5, p < 0.001) was associated with gastrointestinal cancer. Patients with a non-localized tumor at diagnosis had a two-fold risk of suicide and the rate was higher among patients undergoing no treatment, or treatment with chemotherapy or hormones only. It was estimated that 23% of all suicides among male cancer patients and 46% among female cancer patients was associated with the patients having cancer. neoplasms; suicide
In 1973, the death rate from suicide was in the range 0.1-36.9 per 100,000 person-years in different countries (1). In Finland the rate was 23.5, one of the highest in the world. The risk of suicide is high among males, older age groups and those previously married (2). An increased risk is also found among those with neuropsychiatric diagnoses or serious chronic diseases (3). The purpose of this paper is to evaluate the risk of suicide among cancer patients. In Finland about 12,000 new cases of cancer (6000 males and 6000 females) are diagnosed annually. The leading anatomical sites among males are the lung (one third of all new cases of cancer), stomach (15 per cent) and prostate (8 per cent). The leading sites among females are the
breast (20 per cent), stomach (12 per cent) and uterine cervix (7 per cent) (4). MATERIALS AND METHODS
The series originates from the Finnish Cancer Registry. Every case of cancer diagnosed in Finland has been reported to the Finnish Cancer Registry since 1953. The present series consists of cancer cases diagnosed in 1955, 1960 and 1965, a total of 28,857 cases (14,427 males and 14,430 females). The series was followed up to the end of 1970; by that time, 63 cancer patients had committed suicide. The person-years lived by the 28,857 patients were evaluated according to the age of the patient, calendar period and length of the follow-up period. The expected number of cases was estimated for each age-calendar period group by multiplying the number of person-years by the age- and calendar period-specific death rate from suicide for the total Finnish population. The observed number of deaths was found by identifying all the suicides among cancer patients who died from violent causes. The sex, age, and marital status of the
Received for publication February 21,1978, and in final form June 21, 1978. From the Finnish Cancer Registry, Helsinki, Finland, and the Department of Public Health, University of Tampere, Tampere, Finland. Send requests for reprints to M. Hakama, Professor of Epidemiology, Finnish Cancer Registry, Liisankatu 21 B, SF-00170, Helsinki 17, Finland. Supported in part by Red Feather Fund/The Finnish Foundation for Cancer Research. 59
60
LOUHTVUORI AND HAKAMA
cancer patient, the primary site, extent and treatment of the cancer, and the length of the follow-up were taken as suicide risk factors. The series was classified according to the extent of the disease, into those with a localized cancer, i.e., a tumor with no infiltration into neighboring organs or a tumor which had not metastasized to regional or distant lymph nodes, and those with a non-localized disease. Categories of treatment were surgery, radiation, surgery and radiation combined, other treatment and no known treatment. The primary site of the tumor was classified into the broad categories gastrointestinal, respiratory, genital (including breast), and other anatomical organs. The statistical significance between the observed and the expected number of cases was evaluated using the MantelHaenszel test. Whenever the expected number of cases was less than five, exact Poisson probabilities were computed. The effect of the exposure was
evaluated in terms of relative risk (RR = observed number of cases/expected number of cases), etiologic fraction ((RR - 1)/RR) and population etiologic fraction ((RR - 1)/[RR + (1 - a)/a], where a indicates the prevalence of cancer cases in Finland (5)). The prevalence rates were based on data from the Finnish Cancer Registry (4). RESULTS
By the end of 1970, 63 of the registered cancer patients, 49 males and 14 females, had committed suicide. The observed number of suicides was significantly higher than the expected number, which was 38 for males and 7.5 for females. The excess risk of suicide persisted in almost all age- and sex-specific subgroups (figures 1 and 2). The risk of suicide was increased in categories of marital status enough to allow a meaningful comparison (table 1). The risk of married cancer patients committing suicide was twice that for the normal population. The relative risk for
AGE
FIGURE 1. The observed and expected number of suicides in 1955-1970 among male cancer patients diagnosed in Finland in 1955, 1960 and 1965, by age.
61
RISK OF SUICIDE AMONG CANCER PATIENTS
EXPECTED OBSERVED
AOE
FIGURE 2. The observed and expected number of suicides in 1955-1970 among female cancer patients diagnosed in Finland in 1955, 1960 and 1965, by age. TABLE 1
The observed and expected numbers of suicides in 1955-1970 among cancer patients diagnosed in Finland in 1955, 1960 and 1965, by sex and marital status Women
Men Marital status
Obe.
Exp.
O/E5
Obs.
Exp.
O/E
Unmarried Married Divorced or widowed Unknown
1 33* 8 7
L9 19.7 3.1 13.7
0.5 1.7 2.6 0.5
1 5 7* 1
0.8 2.8 1.2 2.8
1.3 1.8 5.8 0.4
Total
49t
38.0
1.3
14*
7.5
1.9
§ O/E = Observed/Expected (Relative Risk), • p < 0.001.
tp
