Improving the measurement of quality of life in older people: the York SF-12

To assess whether changing the layout of the SF-12 affected item response rates, we tested two SF-12 formats in a quasi-randomized trial of women aged >=70 years in two general practices in North Yorkshire. The modified version of the SF-12 (‘York SF-12’) converted the ‘stem and leaf’ format of some questions to individual items. We assessed the effect of the two types of questionnaires on item response rates. The difference in overall response rates to the two questionnaires (York SF-12 26.8%; SF-12 29.5%) was not statistically significant (95%CI -1.88% to 7.22%). However, the modified SF-12 had a statistically significantly lower item non-response rate of 8.5%, compared with the 26.6% of the SF-12 (95%CI 11.1%–25.1%). Chronbach's alpha reliability scores for the York SF-12 were also slightly better than for the older version. The York version of the SF-12 is an improvement on the original questionnaire. We recommend that the York SF-12 be used in preference to the SF-12 when surveying an older population.