Dementia and ageing. An epidemiological study of the detection, preclincal phase, course and prognosis of dementia at age 85 to 88

Abstract

A representative population sample living in the community or in institutions in the city of Gothenburg, Sweden, was followed from the age of 85 (N=494) to 88 (N=248). Methods included a neuropsychiatric and physical examination, key informant interview, MMSE and computerized tomography of the head. Medical records and death certificates were studied. The survey was part of the gerontological and geriatric population studies in Gothenburg (H70).I. The prevalence of dementia in the age group under study increased from age 85 to age 88 in women (from 31% to 46%) but not in men (from 27% to 25%).The increase was mostly attributed to a higher rate of new cases among women than among men. The proportion of moderate to severe dementia increased and cases of mild dementia decreased, mainly due to progression of mild dementias to more severe forms and to the fact that most new cases were of moderate to severe degree. The proportion of vascular dementia was 47% at age 85 and 54% at 88, despite a higher mortality in vascular dementia than in other dementias.II. Sixty-three subjects (18.2%) became demented between age 85 and 88, giving an incidence of 90.1/1000/year for both sexes combined (61.3/1000/year for men and 102.7/1000/year for women; p=0.085). The incidence of Alzheimer´s disease was 36.3/1000/year, vascular dementia 39.0/1000/year (p=1.000) and other dementias 9.1/1000/year. III. Both Alzheimer´s disease and vascular dementia were preceded by a large number of cognitive impairments (e.g., in memory, abstract reasoning, orientation, naming fingers, concentration), psychiatric manifestations (e.g., compulsions, visual hallucinations, increased suspiciousness), behavioral changes (e.g., flattened affects, emotional bluntness, decreased self-confidence, aggressiveness) and subcortical signs (e.g., tremor, psychomotor retardation). The preclinical phase of Alzheimer´s disease was characterised by disturbances in memory, while the preclinical phase of vascular dementia was not.IV. At the age of 85, the non-demented subjects had a mean score of 27.7 on MMSE, and demented individuals scored a mean of 14.5 (p<0.001). More than half of those with mild dementia scored above the cut-off score 23/24. Of the non-demented, 75% scoring below 24 and 37% of those scoring 24 to 25 became demented during the follow-up. Non-demented subjects who did not develop dementia had a mean decline in MMSE-score of 0.6 per year, while those who became demented declined by 2.3 points per year. A decrease of 4 or more points during the three years had a sensitivity of 82% and a specificity of 80%. Correlation was found between MMSE scores and education both in non-demented and demented individuals.V. Among 20 mental and physical disorders studied, Alzheimer s disease and vascular dementia were the most important predictors of seven-year mortality in 85-year-olds, predicting 31 % of all deaths in men and 50 % of all deaths in women, according to a calculation of population attributable risk (PAR). Life expectancy decreased with dementia severity. Survival in women with mild Alzheimer´s disease was similar to that of non-demented women.