Change in suicide rates for patients with schizophrenia in Denmark, 1981-97: nested case-control study
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《英国医生杂志》
1 Bispebjerg Hospital, Department of Psychiatry, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark, 2 National Centre for Register-based Research, University of Aarhus, Taasingegade 1, DK-8200 Aarhus N, Denmark
Correspondence to: M Nordentoft merete.nordentoft@dadlnet.dk
Abstract
In 1980, the suicide rate in Denmark peaked and reached a level that was among the highest in the world, with 34 suicides per 100 000 inhabitants. After 1980 the number of suicides decreased each year, and in 1997 the rate was 15 per 100 000 inhabitants, a 56% reduction.
In Denmark, about half of the people who commit suicide have previously been admitted to psychiatric departments and more than a quarter have been admitted during the past year.1 2 It is consistently reported from several countries that the standardised mortality (standardised for age and sex) for suicide in people with schizophrenia is high,3 4 and in a meta-analysis Palmer et al found that the lifetime risk of suicide among patients after a first admission for schizophrenia was 5.6%.5 Danish and Swedish analyses have shown an increasing rate of suicide among women with a diagnosis of schizophrenia, while the suicide rate has declined in the general population.6-8 The increasing standardised mortality rates for suicide among the most severely mentally ill people have played an important part in the debate about the organisation of psychiatric treatment and prevention of suicide in Denmark and other countries.9
We investigated the suicide rates among patients with schizophrenia and related disorders to see if there was a similar reduction to that seen in the general suicide rate in Denmark from 1981 to 1997. We hypothesised that the ratio between suicide rates in people with a diagnosis of schizophrenia and related disorders compared with suicide rates in the general population would increase.
Methods
The crude suicide rates in the general population fell from 1981 to 1997 (fig 1). Among those who had been admitted to psychiatric hospitals or departments in the same period, there were 756 suicides among patients with schizophrenia, 633 suicides among patients with other psychosis within the schizophrenia spectrum, and 276 suicides among patients with non-psychotic schizophrenia spectrum disorder. Figure 2 shows the incidence rate ratios for suicide, adjusted for age and sex, for patients with these diagnoses. During the period from 1981 to 1997, the incidence rate ratio for suicide among patients with schizophrenia was about 20 times higher than in the general population. We fitted a regression line expressing the change from 1981 to 1997 relative to the general population for each diagnostic group. The lines had slopes of 0.99 (95% confidence interval 0.97 to 1.01, P = 0.3) for schizophrenia, 0.95 (0.93 to 0.97, P < 0.0001) for other psychosis, and 0.99 (0.96 to 1.04, P = 0.9) for schizophrenia spectrum disorders, indicating that for patients with schizophrenia and non-psychotic schizophrenia spectrum disorder, the decrease was similar to the decrease in the general population, while the suicide rate among patients with other psychosis in the schizophrenia spectrum fell faster than in the general population.
Fig 1 Number of suicides per 100 000 inhabitants in Denmark, 1981-97
Fig 2 Incidence rate ratio for suicide in patients with schizophrenia and related disorders, relative to general population. Adjusted for age and sex
We adjusted the incidence rate ratio for suicide for social and demographic risk factors and for time since admission and included age as an interaction term. We then fitted a regression line expressing the change from 1981 to 1997 relative to the general population, adjusted for confounding factors, and for all diagnostic groups there was a linear trend (2 76.24, df = 64, P = 0.14). The table shows the results of the analyses for both sexes and for men and women separately. We mutually adjusted the incident rate ratios for different variables. As in the non-adjusted analyses we found that for patients with schizophrenia and non-psychotic schizophrenia spectrum disorder, the decrease was similar to the decrease in the general population, while the decrease for patients with other psychosis in schizophrenia spectrum was faster; this change was explained by a faster reduction in suicide rate among male patients with these diagnoses compared with the general population (see the results by sex).
Incidence rate ratio for suicide among patients with schizophrenia and related disorders, adjusted for social and demographic risk factors* and for interaction with age by diagnosis, compared with the general population. Figures are incidence rate ratios (95% confidence intervals)
The risk of suicide was high in all diagnostic groups during an inpatient stay and during the first month after discharge, and the longer the time a patient had been discharged, the lower the risk of suicide. Patients who were admitted for the first time during the previous year had a 59% higher risk of suicide compared with other patients.
For patients with schizophrenia, the excess suicide mortality (relative to the general population) decreased with increasing age. We chose patients aged 30 years as reference category and incidence rate ratio was 0.97 (95% confidence interval 0.96 to 0.98) per year. This means that for patients with schizophrenia, the excess suicide mortality is reduced by 3% on average for each year added to the patient's age until 75 years. Thus, the incidence rate ratio of suicide compared with the risk in the general population for two patients aged 30 years and 40 years, respectively, both diagnosed with schizophrenia, currently admitted, and sharing all other characteristics, is 18.00 for the one aged 30 years and 13.27 (18.00x0.9710) for the one aged 40 years.
We adjusted the analysis for confounding with risk, social, and demographic factors known to be of importance in the general population. Adjustment for social and demographic risk factors reduced the incidence rate ratio for suicide among patients with schizophrenia from 21.37 to 12.26. Thus, social and demographic factors explain some of the increased suicide risk for schizophrenia, but even after we controlled for social and demographic factors, suicide was 12 times more common among patients with schizophrenia than in a matched group in the general population.
The table also shows the results of the study for each sex separately. In the general population the suicide rate among men is about twice as high as in women. The incidence rate ratio of suicide for women with schizophrenia and related disorders is higher than for men for all diagnostic groups and for all phases of treatment. This does not mean that the suicide rate for female patients is higher than for male patients, but it indicates a weaker effect of schizophrenia and related disorders among men. For both sexes, the decrease is similar to the decrease in the general population, except that men with other psychoses in the schizophrenia spectrum had a faster decrease in suicide rate than men in the general population.
Discussion
Mortensen PB, Agerbo E, Erikson T, Qin P, Westergaard-Nielsen N. Psychiatric illness and risk factors for suicide in Denmark. Lancet 2000;355: 9-12.
Qin P, Agerbo E, Mortensen PB. Suicide risk in relation to socioeconomic, demographic, psychiatric, and familial factors: a national register-based study of all suicides in Denmark, 1981-1997. Am J Psychiatry 2003;160: 765-72.
De Hert M, Peuskens J. Psychiatric aspects of suicidal behaviour. In: Hawton K, Van Heeringen K, eds. The international handbook of suicide and attempted suicide. Chistester: Wiley, 2000: 121-34.
Black DW, Warrack G, Winokur G. The Iowa record-linkage study. Arch Gen Psychiatry 1985;42: 71-5.
Palmer BA, Pankratz VS, Bostwicj JM. The lifetime risk of suicide in schizophrenia: a reexamination. Am J Psychiatry (in press).
Mortensen PB, Juel K. Mortality and causes of death in first admitted schizophrenic patients. Br J Psychiatry 1993;163: 183-9.
Osby U, Correia N, Brandt L, Ekbom A, Sparen P. Time trends in schizophrenia mortality in Stockholm county, Sweden: cohort study. BMJ 2000;321: 483-4.
Rossau CD, Mortensen PB. Risk factors for suicide in patients with schizophrenia: nested case-control study. Br J Psychiatry 1997;171: 355-9.
Munk-Jorgensen P. Has deinstitutionalization gone too far? Eur Arch Psychiatry Clin Neurosci 1999;249: 136-43.
Malig C. The civil registration system in Denmark: technical papers of the international institute for vital registration and statistics. Bethesda, MA: IIVRS, 1996.
Sundhedsstyrelsen (Danish National Board of Health). Causes of death in Denmark 1980. 1st ed. Copenhagen: Danish National Board of Health, 1982.
Munk-Jorgensen P, Mortensen PB. The Danish psychiatric central register. Dan Med Bull 1997;44: 82-4.
Danmarks Statistik (Danish National Bureau of Statistics). IDA en integreret database for arbejdsmarkedsforskning. Copenhagen: Denmark's Statistics Press, 1991.
Agerbo E, Mortensen PB, Eriksson T, Qin P, Westergaard-Nielsen N. Risk of suicide in relation to income level in people admitted to hospital with mental illness: nested case-control study. BMJ 2001;322: 334-5.
Qin P, Agerbo E, Westergard-Nielsen N, Eriksson T, Mortensen PB. Gender differences in risk factors for suicide in Denmark. Br J Psychiatry 2000;177: 546-50.
Clayton D, Hills M. Statistical models in epidemiology. Oxford: Oxford University Press, 1993.
Sundhedsstyrelsen (Danish National Board of Health). Forslag til national handlingsplan for forebyggelse af selvmord og selvmordsfors?g i Danmark. 1st ed. Copenhagen: Sundhedsstyrelsen, 1998.
Ministry of Social Affairs MotIaH. Government status report on services for the mentally ill 2000. Copenhagen: Statens Information, 2002.
Appleby L, Dennehy JA, Thomas CS, Faragher EB, Lewis G. Aftercare and clinical characteristics of people with mental illness who commit suicide: a case-control study. Lancet 1999;353: 1397-400.
Copas JB, Robin A. Suicide in psychiatric in-patients. Br J Psychiatry 1982;141: 503-11.
Roy A. Suicide in chronic schizophrenia. Br J Psychiatry 1982;141: 171-7.(Merete Nordentoft, associ)
Correspondence to: M Nordentoft merete.nordentoft@dadlnet.dk
Abstract
In 1980, the suicide rate in Denmark peaked and reached a level that was among the highest in the world, with 34 suicides per 100 000 inhabitants. After 1980 the number of suicides decreased each year, and in 1997 the rate was 15 per 100 000 inhabitants, a 56% reduction.
In Denmark, about half of the people who commit suicide have previously been admitted to psychiatric departments and more than a quarter have been admitted during the past year.1 2 It is consistently reported from several countries that the standardised mortality (standardised for age and sex) for suicide in people with schizophrenia is high,3 4 and in a meta-analysis Palmer et al found that the lifetime risk of suicide among patients after a first admission for schizophrenia was 5.6%.5 Danish and Swedish analyses have shown an increasing rate of suicide among women with a diagnosis of schizophrenia, while the suicide rate has declined in the general population.6-8 The increasing standardised mortality rates for suicide among the most severely mentally ill people have played an important part in the debate about the organisation of psychiatric treatment and prevention of suicide in Denmark and other countries.9
We investigated the suicide rates among patients with schizophrenia and related disorders to see if there was a similar reduction to that seen in the general suicide rate in Denmark from 1981 to 1997. We hypothesised that the ratio between suicide rates in people with a diagnosis of schizophrenia and related disorders compared with suicide rates in the general population would increase.
Methods
The crude suicide rates in the general population fell from 1981 to 1997 (fig 1). Among those who had been admitted to psychiatric hospitals or departments in the same period, there were 756 suicides among patients with schizophrenia, 633 suicides among patients with other psychosis within the schizophrenia spectrum, and 276 suicides among patients with non-psychotic schizophrenia spectrum disorder. Figure 2 shows the incidence rate ratios for suicide, adjusted for age and sex, for patients with these diagnoses. During the period from 1981 to 1997, the incidence rate ratio for suicide among patients with schizophrenia was about 20 times higher than in the general population. We fitted a regression line expressing the change from 1981 to 1997 relative to the general population for each diagnostic group. The lines had slopes of 0.99 (95% confidence interval 0.97 to 1.01, P = 0.3) for schizophrenia, 0.95 (0.93 to 0.97, P < 0.0001) for other psychosis, and 0.99 (0.96 to 1.04, P = 0.9) for schizophrenia spectrum disorders, indicating that for patients with schizophrenia and non-psychotic schizophrenia spectrum disorder, the decrease was similar to the decrease in the general population, while the suicide rate among patients with other psychosis in the schizophrenia spectrum fell faster than in the general population.
Fig 1 Number of suicides per 100 000 inhabitants in Denmark, 1981-97
Fig 2 Incidence rate ratio for suicide in patients with schizophrenia and related disorders, relative to general population. Adjusted for age and sex
We adjusted the incidence rate ratio for suicide for social and demographic risk factors and for time since admission and included age as an interaction term. We then fitted a regression line expressing the change from 1981 to 1997 relative to the general population, adjusted for confounding factors, and for all diagnostic groups there was a linear trend (2 76.24, df = 64, P = 0.14). The table shows the results of the analyses for both sexes and for men and women separately. We mutually adjusted the incident rate ratios for different variables. As in the non-adjusted analyses we found that for patients with schizophrenia and non-psychotic schizophrenia spectrum disorder, the decrease was similar to the decrease in the general population, while the decrease for patients with other psychosis in schizophrenia spectrum was faster; this change was explained by a faster reduction in suicide rate among male patients with these diagnoses compared with the general population (see the results by sex).
Incidence rate ratio for suicide among patients with schizophrenia and related disorders, adjusted for social and demographic risk factors* and for interaction with age by diagnosis, compared with the general population. Figures are incidence rate ratios (95% confidence intervals)
The risk of suicide was high in all diagnostic groups during an inpatient stay and during the first month after discharge, and the longer the time a patient had been discharged, the lower the risk of suicide. Patients who were admitted for the first time during the previous year had a 59% higher risk of suicide compared with other patients.
For patients with schizophrenia, the excess suicide mortality (relative to the general population) decreased with increasing age. We chose patients aged 30 years as reference category and incidence rate ratio was 0.97 (95% confidence interval 0.96 to 0.98) per year. This means that for patients with schizophrenia, the excess suicide mortality is reduced by 3% on average for each year added to the patient's age until 75 years. Thus, the incidence rate ratio of suicide compared with the risk in the general population for two patients aged 30 years and 40 years, respectively, both diagnosed with schizophrenia, currently admitted, and sharing all other characteristics, is 18.00 for the one aged 30 years and 13.27 (18.00x0.9710) for the one aged 40 years.
We adjusted the analysis for confounding with risk, social, and demographic factors known to be of importance in the general population. Adjustment for social and demographic risk factors reduced the incidence rate ratio for suicide among patients with schizophrenia from 21.37 to 12.26. Thus, social and demographic factors explain some of the increased suicide risk for schizophrenia, but even after we controlled for social and demographic factors, suicide was 12 times more common among patients with schizophrenia than in a matched group in the general population.
The table also shows the results of the study for each sex separately. In the general population the suicide rate among men is about twice as high as in women. The incidence rate ratio of suicide for women with schizophrenia and related disorders is higher than for men for all diagnostic groups and for all phases of treatment. This does not mean that the suicide rate for female patients is higher than for male patients, but it indicates a weaker effect of schizophrenia and related disorders among men. For both sexes, the decrease is similar to the decrease in the general population, except that men with other psychoses in the schizophrenia spectrum had a faster decrease in suicide rate than men in the general population.
Discussion
Mortensen PB, Agerbo E, Erikson T, Qin P, Westergaard-Nielsen N. Psychiatric illness and risk factors for suicide in Denmark. Lancet 2000;355: 9-12.
Qin P, Agerbo E, Mortensen PB. Suicide risk in relation to socioeconomic, demographic, psychiatric, and familial factors: a national register-based study of all suicides in Denmark, 1981-1997. Am J Psychiatry 2003;160: 765-72.
De Hert M, Peuskens J. Psychiatric aspects of suicidal behaviour. In: Hawton K, Van Heeringen K, eds. The international handbook of suicide and attempted suicide. Chistester: Wiley, 2000: 121-34.
Black DW, Warrack G, Winokur G. The Iowa record-linkage study. Arch Gen Psychiatry 1985;42: 71-5.
Palmer BA, Pankratz VS, Bostwicj JM. The lifetime risk of suicide in schizophrenia: a reexamination. Am J Psychiatry (in press).
Mortensen PB, Juel K. Mortality and causes of death in first admitted schizophrenic patients. Br J Psychiatry 1993;163: 183-9.
Osby U, Correia N, Brandt L, Ekbom A, Sparen P. Time trends in schizophrenia mortality in Stockholm county, Sweden: cohort study. BMJ 2000;321: 483-4.
Rossau CD, Mortensen PB. Risk factors for suicide in patients with schizophrenia: nested case-control study. Br J Psychiatry 1997;171: 355-9.
Munk-Jorgensen P. Has deinstitutionalization gone too far? Eur Arch Psychiatry Clin Neurosci 1999;249: 136-43.
Malig C. The civil registration system in Denmark: technical papers of the international institute for vital registration and statistics. Bethesda, MA: IIVRS, 1996.
Sundhedsstyrelsen (Danish National Board of Health). Causes of death in Denmark 1980. 1st ed. Copenhagen: Danish National Board of Health, 1982.
Munk-Jorgensen P, Mortensen PB. The Danish psychiatric central register. Dan Med Bull 1997;44: 82-4.
Danmarks Statistik (Danish National Bureau of Statistics). IDA en integreret database for arbejdsmarkedsforskning. Copenhagen: Denmark's Statistics Press, 1991.
Agerbo E, Mortensen PB, Eriksson T, Qin P, Westergaard-Nielsen N. Risk of suicide in relation to income level in people admitted to hospital with mental illness: nested case-control study. BMJ 2001;322: 334-5.
Qin P, Agerbo E, Westergard-Nielsen N, Eriksson T, Mortensen PB. Gender differences in risk factors for suicide in Denmark. Br J Psychiatry 2000;177: 546-50.
Clayton D, Hills M. Statistical models in epidemiology. Oxford: Oxford University Press, 1993.
Sundhedsstyrelsen (Danish National Board of Health). Forslag til national handlingsplan for forebyggelse af selvmord og selvmordsfors?g i Danmark. 1st ed. Copenhagen: Sundhedsstyrelsen, 1998.
Ministry of Social Affairs MotIaH. Government status report on services for the mentally ill 2000. Copenhagen: Statens Information, 2002.
Appleby L, Dennehy JA, Thomas CS, Faragher EB, Lewis G. Aftercare and clinical characteristics of people with mental illness who commit suicide: a case-control study. Lancet 1999;353: 1397-400.
Copas JB, Robin A. Suicide in psychiatric in-patients. Br J Psychiatry 1982;141: 503-11.
Roy A. Suicide in chronic schizophrenia. Br J Psychiatry 1982;141: 171-7.(Merete Nordentoft, associ)