Dementia Is a Death Sentence

Abstract & Commentary

By Allan J. Wilke, MD, Residency Program Director, Associate Professor of Family Medicine, University of Alabama at Birmingham School of Medicine—Huntsville Regional Medical Campus, Huntsville. Dr. Wilke reports no financial relationship to this field of study.

Synopsis: The onset of dementia heralds death in about 4½ years.

Source: Xie J, et al. Survival times in people with dementia: analysis from population based cohort study with 14 year follow-up. BMJ. 2008;336:258-262. Jan 10 [Epub ahead of print]

While it is accepted that people with dementia have truncated life spans, reported survival times vary from 3 to 9 years. These researchers, using Great Britain's Medical Research Council's Cognitive Function and Ageing Study (MRC CFAS), a multicenter, longitudinal, prospective, population-based, epidemiological study, sought to clarify the issue. The strengths of this database are its size (13,004 participants), its representation (community-dwelling and institutionalized), its prospective design, and its long follow-up (14 years). The participants, who were free of dementia at the time of enrollment, were interviewed and examined. They were re-examined at two-year intervals. Factors associated with mortality present in earlier studies (age, sex, marital status, place of habitation, education level, social class, functional status, self assessment of health, and living in a deprived neighborhood) were recorded. The researchers did not distinguish between types of dementia.

During the study, there were 438 incident cases of dementia (71% female), and 356 of these 438 (81%) died. Dementia was diagnosed at median age 84 years for women and 83 for men. Death occurred at a median age of 90 for women and 87 for men. Both of these were statistically significant. The median survival time for all was 4.5 years (4.6 years for women, 4.1 for men). In multivariate analysis, male gender (Hazard Ratio [HR] 1.4), age at onset, and degree of dementia predicted shorter survival. Place of habitation, marital status, and mini-mental state examination (MMSE) score did not.

Commentary

As a medical director of a nursing home, I complete death certificates weekly. Although patients with dementia sometimes die of other diseases, such as pneumonia, frequently they just "dwindle" away. When this happens, I list "Dementia" as the proximal cause of death. If you are willing to accept that the results of this study, performed in Great Britain, are applicable in your practice, you have been given a valuable tool to use in your practice with patients and their families. A study performed at Group Health Cooperative, Seattle, WA came to similar conclusions. As devastating as a diagnosis of dementia can be, the uncertainty of how long the patient will be afflicted is also important. Health planners will find this information useful, too.

Curiously, this article was not explicit in the gender breakdown of the cohort. This makes it difficult to say precisely how gender affects the outcome. Using data from an earlier report from this group, we can estimate that about 60% of the cohort was female.

You may be confused why degree of dementia was significant, but MMSE wasn't. Some of this relates to how dementia was measured and what MMSE measures. The researchers used the Blessing Dementia Scale to measure functional performance, including some Activities of Daily Living and changes in personality. MMSE measures cognitive function. As functional capacity declines, demented patients are more likely to become bedbound and less likely to maintain adequate nutrition. Death is surely close behind.