Reliable information on rate of progression of cognitive impairment in probable Alzheimer's disease (AD) is important for evaluating possible beneficial effects of therapeutic agents and in planning long-term care for patients with this chronic illness. However, wide variability exists in published rates of change for psychometric measures of the dementing process, and there is need for an accurate analysis of large numbers of persons with the disorder studied over long periods. Utilizing the large, well-characterized sample of the Consortium to Establish a Registry for Alzheimer's Disease and employing a least squares regression method to adjust for different levels of impairment and periods of observation, we report rates of change on the Short Blessed Test, Mini-Mental State Examination, Blessed Dementia Scale, Clinical Dementia Rating, and other cognitive measures in 430 patients with probable AD (mean age at entry = 70.9 +/- 8.0 SD years) studied for up to 4 years. We found that rate-of-change determinations are less reliable when the observation period is 1 year or less, that dementia progression may be nonlinear when described by certain measures, and that simple change scores do not accurately characterize the rate of decline. We also found that rate of progression in AD is determined by the severity of cognitive impairment: the less severe the dementia, the slower the rate of decline.

The development of Alzheimer's disease (AD) later in life may be reflective of environmental factors operating over the course of a lifetime. Educational and occupational attainments have been found to be protective against the development of the disease but participation in activities has received little attention. In a casecontrol study, we collected questionnaire data about 26 nonoccupational activities from ages 20 to 60. Participants included 193 people with probable or possible AD and 358 healthy controlgroup members. Activity patterns for intellectual, passive, and physical activities were classified by using an adaptation of a published scale in terms of ''diversity'' (total number of activities), ''intensity'' (hours per month), and ''percentage intensity'' (percentage of total activity hours devoted to each activity category). The control group was more active during midlife than the case group was for all three activity categories, even after controlling for age, gender, income adequacy, and education. The odds ratio for AD in those performing less than the mean value of activities was 3.85 (95% confidence interval: 2.65-5.58, P < 0.001). The increase in time devoted to intellectual activities from early adulthood (20 -39) to middle adulthood (40 -60) was associated with a significant decrease in the probability of membership in the case group. We conclude that diversity of activities and intensity of intellectual activities were reduced in patients with AD as compared with the control group. These findings may be because inactivity is a risk factor for the disease or because inactivity is a reflection of very early subclinical effects of the disease, or both.case-control study ͉ dementia ͉ epidemiology ͉ leisure ͉ recreation

To assess the occurrence and related features of motor vehicle crashes in patients with dementia of the Alzheimer type (DAT) we studied 30 patients who had been followed longitudinally and 20 healthy age-matched control subjects. Data were gathered from first-degree relatives who had lived with the subjects for the previous 5 years or more. Forty-seven percent of the DAT patients incurred at least one crash while they were driving, whereas only 10% of the control subjects had had a crash in the previous 5 years. The odds ratio for crashes in the DAT group was 7.9 (p less than 0.01). Moreover, in 77% of DAT patients, a deterioration in driving performance was noted, and 63% of the patients had stopped driving. However, only 42% of the DAT patients who stopped driving did so before a crash occurred. Mean illness duration was 4.0 (+/- 1.8) years, and the mean Mini-Mental Status Examination score was 19.9 (+/- 6.3) at the time of the first crash in the DAT group. The occurrence of crashes was not significantly correlated with dementia severity or with disease duration. These data suggest that the occurrence of driving crashes in patients with DAT is an important public health problem.