Validity and sensitivity of visual analogue scales in young and older healthy subjects.

BACKGROUND Previous findings from studies on the acute effects of drugs indicate that older subjects report less change on visual analogue scales than do younger subjects, when the observed drug effects on objective performance measures are as great or greater. AIM To validate the use of visual analogue scales independently of internal perceptions. SUBJECTS AND METHODS 50 younger and 50 older subjects rated attributes of four animals--tortoise, crow, tiger and wasp--on a series of 10 cm lines. The attributes rated included physical qualities (size, noise) and psychological aspects (danger). RESULTS Ratings were generally similar for the two groups, although older subjects tended to rate slightly greater differences between animals, but the variability was also slightly greater. Thus the mean difference between tiger and wasp for 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 the use of visual analogue scales in both groups. Explanations for the previously observed discrepancy may need to be sought in terms of an effect of age on the perception of internal changes rather than on any difference in the use of the scales.