The pattern of cognitive symptoms predicts time to dementia onset.

Background: Few studies have examined whether cognitive symptom patterns differ by age and length of time before dementia onset. Our objective was to investigate whether different patterns of cognitive symptoms at ages 70, 75, and 79 years predict short-term (< or =5 years) and long-term (>5 years) dementia onset.

Methods: A representative sample of 382 nondemented 70-year-olds from Gothenburg, Sweden was examined periodically up to age 90 years. Information on dementia in those lost to follow-up was obtained from medical records. Cognitive assessments at ages 70, 75, and 79 years included psychiatric and psychometric examinations. Four patterns of cognitive performance were examined in relation to dementia onset: (1) unimpaired cognition, (2) isolated low memory, (3) low non-memory, and (4) global low cognitive performance.

Results: Short-term onset was predicted by global low performance at ages 70, 75, and 79 years and by low non-memory performance at ages 70 and 75. Isolated low memory was not a short-term predictor at any examination, but it predicted long-term onset at ages 70 and 75 years.

Conclusions: A global pattern of low cognitive performance predicts short-term but not long-term onset of dementia, whereas isolated low memory performance predicts dementia only in the long-term. Our findings also suggest that preclinical symptoms of dementia might differ by age.