[Association between social environment and aging of the brain: evaluation with the event-related potential P300]

To investigate the association between social environment and aging of the brain, we studied P300 event-related evoked potentials in 95 normal elderly subjects living in different social environments. The subjects were divided into two groups: 22 healthy people living in old-age homes (average age 76.5 +/- 5.6 years, average Hasegawa Dementia Scale-Revised 27.4 +/- 2.5), and 93 healthy people living in their own homes (average age 74.1 +/- 5.4 years, average Hasegawa Dementia Scale-Revised 28.3 +/- 2.3). Target and Novelty P300 were recorded by using an auditory oddball paradigm. There were no differences in risk factors for strokes or in findings on magnetic resonance imaging between the two groups.

Cognitive function (Okabe's Score and Koh's Block Design Test) were lower in those living in an old-age home than in those living in their own homes. Both target and novelty N100 examinations showed no significant differences in amplitude or latencies between the two groups. However, P300 latencies were larger among those living in an old-age home than among those living in their own homes; P300 amplitudes in the two groups were similar. Those living in an old-age home also had greater age-associated declines in function, as shown by longer latencies in target P300 than in novelty P300.

Social-environmental factors are closely associated with the aging of the brain.