Detecting an Early Response to Donepezil With Measures of Visual Attention

Acetylcholinesterase inhibitors (AChE-I) comprise the major class of drugs used to treat Alzheimer's disease (AD). Despite widespread use, there is controversy about the usefulness of these medications. Concerns have been modest response rates of treated versus placebo groups, relatively small effect sizes with respect to efficacy, drug costs, and clinical relevance of the effects. One problem is that measures of efficacy used may not be sufficiently sensitive to detect a true drug effect. Another problem is that changes noted after 4-6 months of therapy confound the drug effect and the natural progression of the disease. Lastly, patient heterogeneity may contribute to the wide range of degree of response, further decreasing overall effect sizes. The investigators address three important issues to improve the clinical usefulness of cholinergic therapy. First, outcome measures are needed that are sensitive to the effects of cholinergic treatment. Second, outcome measures should be sensitive to the drug effect early in the course of treatment before a measurable decline of the disease progression occurs. Third, improved treatment would be attained if specific patient characteristics or performance measures were identified, which contributed to, or even predicted who will likely benefit. The premise of the current proposal is that measures of higher-order attention - currently omitted from standard assessments of treatment outcome - can provide insight into early efficacy of cholinergic treatment. The investigators are conducting a preliminary study that supports our hypotheses by testing the value of such attentional measures. The rationale for using attentional measures is as follows: (1) Attentional deficits are recognized as a critical cognitive change in the earliest phases of AD; (2) Attentional function, particularly tasks that tax available attentional capacity, is mediated by the cholinergic system; and (3) Acetylcholine is depleted in AD. However, the link between attention and cholinergic depletion in AD has not been fully explored, particularly with regard to response to cholinergic treatment. Surprisingly, attentional measures have not been included in the evaluation of AChE-I in the treatment of AD. The investigators propose that attentional performance could serve as a highly sensitive outcome measure and a marker of response.

Study aims and hypotheses

1. To determine that higher-order attentional measures are sensitive to the effect of cholinergic change early in the course of treatment. The investigators predict that performance on attentional tasks will improve in AChE-I treated patients compared to placebo controls after 7±1 weeks of treatment.

2. 2a. To examine the effect of cholinergic treatment on attentional measures as compared with global measures or measures of other cognitive domains. The investigators predict that the performance on tasks of attention is more sensitive than traditional global measures of performance.

2b. To examine whether cholinergic treatment changes the relationships among measures of attention and measures of other cognitive function. The prediction is that that the relationships among attention and cognitive domain measures will change with treatment.