Mohammed T. Abou-Saleh

104 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYhigher risk for being male. This concords with the meta-analysisquoted above for age, but not for sex.A detailed editorial 10 discusses issues in research into depressionand mortality. In particular there is difficulty in separatingassociation from causation.METHODOLOGICAL ISSUESA number of measurement issues have failed to receive appropriateattention. The studies of community samples use differentmethods of measuring differences in risk. Although for low risksthe numerical difference between risk ratios and odds ratios issmall, comparison would be simpler if studies reported in acommon way.Patient studies have not really addressed the issue of biasintroduced by differential identification of the patient group andthe controls. For instance, if date of diagnosis is used as thestarting point for survival analysis, there will be a survivor biasand it will be difficult to identify controls in a similar way.Studies comparing patient groups with the general populationhave also failed to account for the fact that demented people arepart of the population, and if their death rate is very differentfrom that of the population as a whole, and if they form asubstantial part of the population, as they will beyond age 85,then the death rate quoted for the general population is anoverestimate of that expected for non-demented people.Few studies have put their results into any clear framework.For instance, the possibilities raised by epidemiologists 11 studyingchronic physical illness, and implicit in the textbook relationshipbetween prevalence, incidence and duration of illness, have hardlybeen explored 12 .DISCUSSIONMortality has been one of the most studied endpoints inepidemiology, but the reader of the community studies will bestruck by the fact that, for few of them, mortality was a primaryend point. This has undoubtedly created the patchwork ofmethods of reporting which bedevils synthesis.There has been a considerable literature relating mentaldisorders in younger adults to mortality 13 , which has confirmedan increased risk for affective disorders (typical SMR 1.4) andschizophrenias (typical SMR 2.3). The studies quoted here suggesta similar, possibly slightly greater, risk for depression.There is clearly an elevated risk for both dementia anddepression, but there is little that can be confidently assertedbeyond that. We do not know whether the risk is modified byother possible explanatory variables like age, sex, physical illnessof functional status, neither do we know what causes of deathaccount for the excess cases.As yet, we do not know what would happen to mortality if wetreated depression in older age more vigorously, or what wouldhappen if universally effective treatments for dementia becameavailable and we could treat people with dementia.REFERENCES1. Farr W. Report upon the mortality of lunatics. J Statist Soc Lond1841; 4: 17–33.2. Ødegård Ø. Excess mortality of the insane. Acta Psychiat NeurolScand 1952; 27: 353–67.3. Flaten TP. Mortality from dementia in Norway, 1969–83. J EpidemiolCommun Health 1989; 43: 285–9.4. van Dijk PTM, Dippel DWJ, Habbema JDF. Survival of patientswith dementia. J Am Geriat Soc 1991; 39: 603–10.5. Schröppel H. Zur mortalität bei dementiellen and depressivenErkrankungen im Alter. Zeitschr Gerontopsychol Psychiat 1994; 7:179–93.6. Dewey ME, Saz P. Dementia, cognitive impairment and mortality inpersons aged 65 and over living in the community: a systematic reviewof the literature. Int J Geriat Psychiat 2001; 16: 751–71.7. Saz P, Dewey ME. Depression, depressive symptoms and mortality inpersons aged 65 and over living in the community: a systematic reviewof the literature. Int J Geriat Psychiat 2001; 16: 622–63.8. Langley AM. The mortality of mental illness in older age. Rev ClinGerontol 1995; 5: 103–12.9. Jagger C, Clarke M, Stone A. Predictors of survival with Alzheimer’sdisease: a community-based study. Psychol Med 1995; 25: 171–7.10. O’Brien JT, Ames D. Why do the depressed elderly die? Int J GeriatPsychiat 1994; 9: 689–93.11. Haberman S. Mathematical treatment of the incidence and prevalenceof disease. Soc Sci Med 1978; 12: 147–52.12. Dewey ME. Estimating the incidence of dementia in the communityfrom prevalence and mortality results. Int J Epidemiol 1992; 21(3):533–6.13. Tsuang MT, Simpson JC. Mortality studies in psychiatry: should theystop or proceed? Arch Gen Psychiat 1985; 42: 98–103.