ARTHRITIS & RHEUMATISM Vol. 50, No. 3, March 2004, pp 953–960 DOI 10.1002/art.20048 © 2004, American College of Rheumatology Normative Values for the Health Assessment Questionnaire Disability Index Benchmarking Disability in the General Population Eswar Krishnan, 1 Tuulikki Sokka, 2 Arja Ha ¨kkinen, 3 Helen Hubert, 4 and Pekka Hannonen 3 Objective. The Health Assessment Questionnaire (HAQ) disability index (DI) has been commonly used in rheumatology to quantify functional disability in patient groups, but current general population values of this index are not available. This study was undertaken to establish normative values for the HAQ DI in a general population and to analyze its correlates. Methods. The HAQ DI (range of scores 0–3) was measured in a random sample of 1,530 adults in the Central Finland District. Prevalence rates of disability by strata of age, sex, education level, body mass index (BMI), and health behaviors (including smoking and exercise habits) were calculated. Pearson’s product- moment correlation coefficient and ordinary least squares regression were used to analyze the data. Results. The estimated population mean HAQ DI was 0.25 (95% confidence interval 0.22–0.28), and 32% of respondents had at least some disability. Both for men and for women, functional disability increased exponentially with age. The HAQ DI was correlated with pain (r  0.58) and global self assessment (r  0.61). The prevalence of disability decreased with increasing number of years of education, lower BMI, and increasing frequency of physi- cal exercise. Conclusion. Almost one-third of the general pop- ulation has some functional disability. Functional dis- ability is associated in part with lifestyle choices and increases with age in a nonlinear manner. The norma- tive values of the HAQ DI that we have presented could be used as a reference benchmark for clinical and epidemiologic studies using this measure of disability. Over the last 20 years, self reports of functional limitations have become a major component of health status outcomes in rheumatic diseases. The challenge of objectively defining functional disability is not dissimilar to that faced by the protagonist in Robert M. Pirsig’s Zen and the Art of Motorcycle Maintenance, who lost his mind trying to define the concept of “quality” (1). The Health Assessment Questionnaire (HAQ) is one of the most widely used self-assessment instruments for mea- suring functional disability in patients with a variety of rheumatic diseases (2,3). This instrument contains ques- tions on functional limitations from which a valid, effec- tive, and sensitive measure of disability, the HAQ dis- ability index (DI), can be computed. The HAQ is a generic questionnaire in the sense that it does not differentiate between disability caused by arthritis and that caused by other disease conditions. In longitudinal studies of patient populations, functional disability has been observed to increase with time (4–9). However, this increase could be due to sex, age, and age-related comorbidities in addition to disease progression. Discriminating age- and sex-related de- clines in function from those that are disease-related requires normative data (i.e., the HAQ DI in “normal” general populations as opposed to that in patient groups). The dearth of such data has impeded routine use of the HAQ DI in clinical practice. The present report presents normative data on the HAQ DI by age and sex from a general population sample in Finland and compares them with data from other studies Supported in part by the Academy of Finland. 1 Eswar Krishnan, MD, MPhil: Stanford University, Palo Alto, California, and Clinical Research Center of Reading, Reading, Penn- sylvania; 2 Tuulikki Sokka, MD, PhD: Jyva ¨skyla ¨ Central Hospital, Jyva ¨skyla ¨, Finland, and Vanderbilt University, Nashville, Tennessee; 3 Arja Ha ¨kkinen, PhD, Pekka Hannonen, MD, PhD: Jyva ¨skyla ¨ Central Hospital, Jyva ¨skyla ¨, Finland; 4 Helen Hubert, MPH, PhD: Stanford University, Palo Alto, California. Address correspondence and reprint requests to Eswar Krishnan, MD, MPhil, Clinical Research Center of Reading, 401 Buttonwood Street, West Reading, PA 19468. E-mail: eswar_ krishnan@hotmail.com. Submitted for publication April 8, 2003; accepted in revised form November 13, 2003. 953