VALIDITY AND SENSITIVITY OF VISUAL ANALOG SCALES IN YOUNG AND OLDER HEALTHY-SUBJECTS

Background: previous findings from studies on the acute effects of dru gs indicate that older subjects report less change on visual analogue scales than do younger subjects, when the observed drug effects on obj ective performance measures are as great or greater. Aim: to validate the use of visual analogue scales independently of internal perception s. Subjects and methods: 50 younger and 50 older subjects rated attrib utes of four animals-tortoise, crow, tiger and wasp-on a series of 10 cm lines. The attributes rated included physical qualities (size, nois e) and psychological aspects (danger). Results: ratings were generally similar for the two groups, although older subjects tended to rate sl ightly greater differences between animals, but the variability was al so slightly greater. Thus the mean difference between tiger and wasp f or size was 60.1 (SD 15.6) in the younger group and 68.8 (SD 18.4) in the older group. Conclusions: these results support the validity of th e use of visual analogue scales in both groups. Explanations for the p reviously observed discrepancy may need to be sought in terms of an ef fect of age on the perception of internal changes rather than on any d ifference in the use of the scales.