Epidemiology and aetiology

The prevalence of personality disorders in the elderly varies as to the methodology used and the population studied.

Community studies have been the most useful to date. The best community study has been by Cohen and colleagues, using the Epidemiologic Catchment Area ( ECA) data from Baltimore, Maryland.(13) Psychiatrists examined 841 subjects using the semi-structured Standardized Psychiatric Examination to diagnose personality disorders with DSM-III criteria. Comparing those over the age of 55 with those under 55, older individuals were found significantly less likely to have a personality disorder (6.6 to 10.5 per cent) as compared with younger individuals. This finding was almost entirely due to a threefold higher prevalence of cluster B personality disorders in those under the age of 55, especially antisocial and histrionic personality disorders. Interestingly, in this study none of the older individuals were found to have cluster A personality disorders. Table 1 summarizes the findings of this large community study. The strengths of this study were that it was a community rather than a clinical sample, and subjects were evaluated by psychiatrists using a structured questionnaire. Limitations of this study were those inherent to the study of personality disorder in late life, in that older subjects may have been inaccurate in recalling maladaptive behaviours, and outside informants were not used. As well, structured questionnaires may not be valid in diagnosing personality disorder in the elderly. A community survey study of DSM-III personality disorder traits using the

Personality Diagnostic Questionnaire revealed that 'dramatic' and 'anxious' personality traits declined up to 60 years of age with a slight increase thereafter, but that 'odd' or 'eccentric' traits showed no change with age.(14)

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Table 1 Weighted prevalence (%) of DSM-III personality disorders in a large community study

In addition to community samples, specific clinical samples have been examined. A retrospective study of 2322 psychiatric inpatients with major depression found the prevalence of personality disorder to be 11.2 per cent in those over the age of 65 as compared with 17.2 per cent for those under 65. (1.0) There was variability among specific personality diagnoses with age as no diagnoses of borderline personality disorder were found in the elderly, while compulsive personality disorder was actually diagnosed more frequently in the elderly. A study of elderly male veteran inpatients with a variety of non-psychotic psychiatric diagnoses revealed a high prevalence (61 per cent) of personality disorder.(15) The specific population studied and the fact that all were in the midst of a psychiatric illness requiring hospitalization makes this and other inpatient studies of limited value. For example, another inpatient study using elderly male veterans and elderly females from a geropsychiatric ward using the Structured Interview for Disorders of Personality—Revised ( SIDP-R) revealed a personality disorder prevalence of 56.5 per cent in those assessed.(!6) It was noted that actual clinical diagnoses of these patients revealed far fewer Axis II diagnoses than as assessed by the SIDP-R. Methodological issues raised by this study include the possibility of false-positive results in the use of structured instruments—which are developed and validated in younger individuals, as well as in assessing acutely ill psychiatry inpatients.

Unfortunately, outpatient studies have similar limitations when studying those with concurrent Axis I diagnoses. To date, no study exists of non-psychiatric elderly outpatients. A study of 36 psychiatric outpatients, including those with bipolar disorder, delusional disorder, and schizophrenia, revealed that 58 per cent had a diagnosis of personality disorder. (1Z» Arguably, diagnosing personality disorder in the face of these disorders is likely to be difficult and result in an overestimation. There have been a number of studies into the depressed elderly, but, as noted before, depression may exacerbate or conceal personality traits, thus making firm conclusions of personality disorder in such individuals difficult. Despite this, there are valid reasons for studying personality disorders in such populations, for instance to find out whether personality traits predispose to depression in late life or how personality disorder affects the course of depression, or other Axis I disorders. For example, in the young, personality disorder has been associated with poor outcome in depression. In addition, there is some evidence that personality disorder symptoms (specifically avoidant and dependent traits) may negatively affect interpersonal function and instrumental activities of daily living after the depression is treated.(18)

A meta-analysis of 11 articles published from 1980 to 1994 of personality disorders based on DSM-III or DSM-IIIR criteria revealed an approximately 10 per cent prevalence of personality disorders in those aged 50 and over.(19) In comparing these studies it was noted that the method of diagnosis affected the prevalence of personality disorder. Also, a greater prevalence of personality disorders was found in outpatient versus inpatient settings. In conclusion, the authors felt that there was a definite need for well-designed studies using statistically robust samples to assess the true prevalence of personality disorders in late life.

Taking the best studies together—the Cohen community study and the meta-analysis—the prevalence of personality disorder in the elderly, as currently defined, ranges from 7 to 10 per cent, with a decrease in prevalence of cluster B diagnoses.

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