Where Are the Reversible Dementias?

40%. 1 In clinical practice, the numbers of reversible dementia were lower than those reported. In 1988, two separate meta-analyses indicated that the reversibility of dementia occurred much less frequently. 2 In 1995, Weytingh et al. conducted a systematic quantitative review of the literature on reversible dementia to explain the variability from 0% to 25% in the reported incidences of reversible dementia. They concluded that reversible dementia was rare in an outpatient setting and that its pursuit should not be undertaken at the cost of overinvestigating the many other cases of irreversible disease. 3 Physiciansoften orderabatteryoftests toexcludesome of the potentially reversible causes of dementia, which include medications, alcohol abuse, depression, metabolic disorders (thyroid disease, B12 deficiency), and normal pressure hydrocephalus. Is this necessary? In 1988, Dr. Clarfield conducted a critical review of 32 studies (from 1972 to 1987) and found that, of the nearly 3,000 cases of dementia surveyed, at most only 11% reversed: 8% partially and 3% fully. This same author is now reexamining this issue and cited several hypotheses to explain why he believes this estimate of reversibility in the previous meta-analysis was inflated. He posits that bias in the sample derives from the following factors. The mean age of the study patients was younger (72.3) than seen in clinical practice; a referral bias existed favoring enrollment from tertiary care facilities; and there was a lack of stringent study design, such as failing to use standardized instruments in the diagnosis of dementia, blinding, or performing adequate follow-up. (As in many cases, the reversibility was temporary.) Given the wide discrepancy in the percentages of treatable causes of dementia reported in the literature and its implications for clinicians in their evaluation of patients, Dr. Clarfield has undertaken another thorough review of recent literature and presents an updated analysis of reversible dementias and their prevalence. DATA SOURCES: The methodology of the current metaanalysis was similar to that used in the previous study from 1988, with an emphasis on adherence to the guidelines of the Meta-analyses of Observational Studies in Epidemiology (MOOSE) group. 4 A computer search of Index Medicus from 1987 to 2002 was conducted. (Five articles from 1987 not included in the original meta-analysis, have been included in the current review.) A follow-up of the relevant bibliography in the articles identified was also conducted. Standard textbooks of geriatrics, neurology, internal medicine, and psychiatry were also consulted. Key words for the search included dementia, treatable dementia, reversible dementia or dementia, and etiology. STUDY SELECTION CRITERIA: The search of Index Medicus was restricted to English language. All articles that provided data according to the different etiologies of dementia were included. Those that were excluded addressed the issue, but the data could not be extracted from it, for example, if the total number of patients with dementia did not correspond to the sum of the different causes of dementia or if the definition of the etiology was vague. Dr. Clarfield contacted the original authors of the articles, and if the information obtained was relevant, the study was included.