Aims: The aim of this study was to examine the association between assessed
work ability and the duration of certified sickness absence. Methods: A to
tal of 549 patients and 52 doctors provided questionnaire data about 549 ep
isodes of absence. The episodes were classified as new, one month. or three
months according to their duration at the time of questionnaire completion
. Their duration after that was used as outcome. Uni-and multivariate Cox r
egression analyses were performed. Results: In the multivariate analyses, a
"very much reduced" work ability assessed by patients was associated with
a longer duration than a "moderately reduced" work ability, in both one- an
d three-month episodes. Musculoskeletal and psychological, disorders were a
ssociated with a longer duration, and respiratory disorders with a shorter
duration than other disorders in new episodes. Patient age above 50 years w
as associated with a longer duration than lower age in new and three-month
episodes. The doctors' use of referral and tests in the consultations, and
the presence of non-medical factors as judged by the patients, were associa
ted with a longer duration than the absence of those factors in new episode
s. The patients' degree of job satisfaction, and non-medical factors as jud
ged by doctors. were significantly associated with duration only in univari
ate Cox regression analyses in new episodes. Work demands were not signific
antly associated with duration in any of the analyses. Conclusions: Work ab
ility assessed by patients may be a useful prognostic indicator of duration
in prolonged episodes of certified sickness absence. Further studies using
other outcomes, such as disability pensioning, would be of interest to enl
ighten the concepts of work ability.