Source
Journals of Gerontology. Series A, Biological Sciences & Medical
Sciences.
51(3):M116-22, 1996 May.
Abstract
BACKGROUND. Tripping over an obstacle is a common cause of falls in
the elderly. An earlier study of abilities to
avoid stepping on suddenly appearing obstacles found that, although
healthy old adults had a lower rate-of-success than
young adults, the magnitude of that difference was not large. The
present study inquired whether dividing attention during
such a task would differentially affect young and old healthy adults.
METHODS. Rates-of-success were observed in 16
young and 16 old healthy adults (mean ages 24 and 72 years) in
avoiding stepping on a band of light that was suddenly
projected across their gait path while they walked at their
comfortable gait speed. This virtual obstacle was placed at
predicted next-footfall locations to give 350 or 450 msec available
response times before footfall. During most of the
trials the subjects were asked, in addition to trying not to step on
the obstacle, simultaneously to respond vocally as
quickly as possible when red lights near the end of the walkway
turned on. These attention-dividing reaction time tests
were of two types: synchronized, when only red lights lit at
intervals synchronized with the appearance of the obstacle,
and unsynchronized, when green or yellow lights lit in addition to
the red lights, with lighting intervals not synchronized
with the appearance of the obstacle. RESULTS. When synchronized and
unsynchronized reaction time tests were
conducted concurrently with the obstacle avoidance tasks, mean
rates-of-success in avoidance decreased significantly in
both young and old adults. With available response times of 350 msec,
mean success rates decreased from their
no-division values in the young adults by 14.7% for synchronized
reaction and by 19.9% for unsynchronized reaction,
attention-dividing tests. Corresponding mean decreases for the old
adults were 32.0 and 35.7%. This age difference in
the effects of dividing attention was significant. CONCLUSION. Both
young and old adults had a significantly increased
risk of obstacle contact while negotiating obstacles when their
attention was divided, but dividing attention degraded
obstacle avoidance abilities of the old significantly more than it
did in the young. Diminished abilities to respond to
physical hazards present in the environment when attention is
directed elsewhere may partially account for high rates of
falls among the elderly.