Staring into space, disorganized or illogical thinking, and unusual daytime sleepiness suggest a greater risk for Alzheimer’s in older people, a new study reveals (Neurology. 2010;74:210-217).

Investigators examined data from 511 men and women, aged 51 to 101 years, who were enrolled in a longitudinal study of memory and aging. Testing assessed cognitive fluctuations (mental lapses), which are spontaneous alterations in cognition, attention, and arousal. Cognitive fluctuations are a core feature of Lewy body dementia—thought to be the second most common form of dementia after Alzheimer’s—but the impact of these lapses were unknown when this study began.

Study participants and knowledgeable sources (usually a spouse or adult child) were asked whether the subject experienced any of the following: (1) Drowsiness and lethargy all the time or several times a day despite having gotten enough sleep the night before (daytime somnolence); (2) daytime sleep of two or more hours before 7 p.m.; (3) episodes in which the person’s flow of ideas seemed disorganized, unclear, or illogical; and (4) episodes of staring into space for long periods.

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A positive response to at least three items suggests cognitive fluctuations.

Fluctuations were present in 12% of the participants with Alzheimer’s disease. Of the 295 individuals with no dementia, only two had mental lapses. Among the remaining 216, who had very mild or mild dementia, 25 had mental lapses. Overall, those with mental lapses were 4.6 times more likely to have dementia than those without. Those who had disorganized, illogical thinking had more than a sevenfold increased risk of being rated as cognitively impaired.

The authors conclude that clinicians evaluating a patient for problems with thinking and memory should consider also assessing them for these mental lapses. “The inclusion of fluctuation scales such as the Mayo Fluctuation Questionnaire [used in this study] in the assessment of older adults for cognitive disorders may capture these clinically important events.”

Another study indicated that otherwise healthy older persons (mean age: 67.2 years) with subjective cognitive impairment were 4.5 times more likely to progress to mild cognitive impairement or dementia over a seven-year period than were persons without these symptoms (Alzheimers Dement. 2010;6:11-24). Subjective cognitive impairment is marked by situations such as when people recognize their declining ability to recall a name or remember where they placed an important object.