Subjective memory complaints, education, and risk of Alzheimer's disease

BACKGROUND: Subjective memory complaints are common in the elderly. Although memory complaints are associated with an increased risk of Alzheimer's disease in persons with cognitive impairment as well as in persons with normal cognition, they are commonly considered of less importance than objective cognitive measures. We hypothesized that the clinical relevance of subjective memory complaints might vary with educational background. METHODS: The study was performed within the Rotterdam Study, a prospective population-based cohort study among 7983 persons 55 years and older. Subjective memory complaints and level of education were assessed in the baseline interview (1990 to 1993). During a mean follow-up of 9.0 years we identified 568 incident Alzheimer's disease patients. We estimated the association between subjective memory complaints and risk of dementia by means of Cox proportional hazard models. RESULTS: The association between subjective memory complaints and risk of Alzheimer's disease varied across levels of education. The risk of Alzheimer's disease associated with subjective memory complaints was higher in highly educated persons (age- and sex-adjusted hazard ratio, 2.33; 95% confidence interval CI, 1.00-5.49) than in persons with a low education (age- and sex-adjusted hazard ratio, 1.53; 95% CI, 1.15-2.05) (P value for interaction, .02). In highly educated persons without objective cognitive impairment (Mini-Mental State Examination score, 29 or 30) the risk of Alzheimer's disease was highest (age- and sex-adjusted hazard ratio, 2.98; 95% CI, 1.76-5.02). CONCLUSIONS: Especially in persons with a high level of education who still perform well on formal cognitive tests, subjective memory complaints might be an important first sign of imminent Alzheimer's disease.