Factors affecting completion of the SF-36 in older people.
OBJECTIVE
to examine the influence of specific clinical impairments and disabilities on the completion of the SF-36 health status measure among older people.


DESIGN
Prospective observational study.


SETTING/PARTICIPANTS
An SF-36 was administered to 245 subjects aged 65 years and older. Subjects were chosen by sampling from a variety of inpatient, outpatient and community sources to ensure a range of relevant disabilities.


MEASUREMENTS
response rates, overall rates of completion, completion of individual questions and time taken to complete.


RESULTS
severe functional impairment (Barthel index < or = 12) was found in 22.4% (51/228), cognitive impairment in 54.1% (132/244), depressed mood in 77.0% (151/196) and visuospatial dysfunction in 71.3% (134/188). The median number of impairments was three (interquartile range 1-4). Specific physical impairments were visual in 13.2% (31/235), hearing in 30.2% (74/245), impaired manual dexterity in 18.0% (44/245) and dysphasia in 23% (55/239). In multivariate analyses, global functional impairment (P = 0.006), cognitive impairment (P = 0.0001) and impaired manual dexterity (P = 0.005) were significantly associated with more dimensions uncompleted, whilst cognitive impairment (P = 0.001), age (P = 0.006) and visuospatial dysfunction (P = 0.0003) were significantly associated with longer completion times.


CONCLUSION
the most striking finding of the study was that global rather than specific physical and mental dysfunction was associated with the inability to complete the SF-36 questionnaire. The difficulty appears to lie in the performance of a complex task, rather than with specific aspects of the task which could be overcome by adaptation or aids. Our experience is that this relatively complex questionnaire does not adequately measure functional health status in disabled older people because of non-completion and may therefore overestimate the health of populations.