Natural history of frontotemporal dementia: comparison with Alzheimer's disease.

INTRODUCTION: Frontotemporal dementia (FTD) is a more common cause of dementia than previously recognised. Few data are available regarding the natural course of FTD in terms of survival, nursing home admission and causes of death.
METHODS: An observational study of all consecutive patients referred to the memory centre of Lille, France, between 1995 and 1999, and examined at least twice in this centre, with a diagnosis of FTD (frontal or behavioural variant) or of Alzheimer's disease (AD) was performed. Kaplan-Meyer analysis allowing for delayed entry was used to compare the survival functions in FTD and AD.
RESULTS: 552 patients were included, of whom 49 (8.9%) were lost to follow-up at 3 years. FTD patients were younger (mean age at onset 59 years), had more often a family history of psychiatric disorders (20%), had a longer delay between first symptoms and first visit (5.9 years) and a higher Mini-Mental State Examination (MMSE) score at first visit (24.5) than patients with AD (19.9). The mean annual MMSE score decline was 0.9 point in FTD vs. 2.0 points in AD (p < 0.0004). Fewer patients with FTD than with AD entered an institution (RR: 0.20, 95% CI 0.05-0.81). After adjustment for sex, age at first visit, level of education and MMSE score at first visit, survival rates in FTD and AD did not differ significantly. Patients with FTD often had a sudden death, the cause of which could not be found. The earlier the first visit after onset, the longer the survival rate, whatever the diagnosis (RR: 0.76, 95% CI 0.67-0.86, p < 0.0001 per year of earlier first visit).
CONCLUSION: This large study showed that the mean duration of FTD was 2 years longer than that of AD, but the risk of death after adjustment for age and sex was similar in FTD and in AD. Sudden and unexplained causes of death were frequent and need further study. Early management increases the life span of demented patients. Copyright 2004 S. Karger AG, Basel