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RESEARCH PRODUCT

Survival in Alzheimer disease

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We thank Dr Lesser for his comments. We agree that deaths in older populations with AD are often from comorbid conditions, and we would not wish to overinterpret the limited survival data from this study. We also accept that determining symptom onset is an inexact science. However, we would suggest that in this small cohort the disease course of about a decade cannot be considered an aggressive one. Since publication of our study, 2 additional subjects have died 8.9 and 16.8 years after onset thereby increasing the mean time from onset to death to 9.4 years. We agree, however, that further study is required to resolve these issues and in particular to assess genetic factors that may influence the rate of disease progression. Although findings in familial AD may not necessarily generalize to sporadic disease, the study of early-onset pedigrees affords the opportunity to assess progression with fewer confounds of comorbidity.