Incidence of dementia in patients with subjective memory complaints

Background: The risk of developing dementia by elderly patients with only subjective memory complaints (SMC) is unclear. Our objective was to assess the prognosis of such patients regarding subsequent development of dementia. Methods: From 1992 to 1996, 211 consecutive patients (age 67.4±9.4 years, mean±SD) were diagnosed as having SMC. These patients were followed for 3 years or to the time they were diagnosed with dementia, whichever came first. A survival analysis was performed for occurrence of dementia within 3 years. Results: The duration of memory decline was shorter among patients who developed dementia than among those who did not (32.6 vs. 49.9 months, F=3.3, p=0.07). Patients who developed dementia tended to be older at the reported onset of memory decline (71 vs. 66.2 years, F=3.2, p=0.07). Lower risk of dementia was associated with higher cognitive performance at entry [odds ratio (OR)=0.74 (0.59–0.92)] and longer time from onset of memory decline to referral [OR=0.91 (0.85–0.98)]. Conclusion: Subjects with SMC have an increased risk of developing dementia, particularly those with lower cognitive status at entry and with older age at onset of memory complaints, and shorter duration of their memory complaints.