title: Effect of a 1-month vs. a 12-month reference period on responses to the 14-item Oral Health Impact Profile.
abstract: The length of the reference period used in surveys of subjective oral health may have a marked influence on the responses obtained. We aimed to evaluate the effect of a 1-month (RP-1) vs. a 12-month (RP-12) reference period in the Oral Health Impact Profile (OHIP-14) questionnaire. Using a randomized cross-over design, RP-1 and RP-12 OHIP-14 questionnaires were administered, 1 month apart, to two samples of Finnish adults, namely people awaiting orthognathic surgery (n = 104) and non-patient workers (n = 111). The effect of the reference period was computed by subtracting RP-1 OHIP-14 severity scores from RP-12 OHIP-14 severity scores (DeltaRP). Potential order effects were assessed by comparing DeltaRP between groups completing the RP-1 vs. the RP-12 questionnaire first. Mean OHIP-14 severity scores were slightly higher when the RP-12 questionnaire was administered first, but mean DeltaRP values were below the value of 2.5 considered clinically meaningful, and all 95% confidence intervals for DeltaRP included zero. No order effects in the OHIP-14 severity scores were observed. Therefore, although a standardized reference period of 12 months is recommended, in population surveys the use of a shorter reference period does not appear to influence responses.
authors.affiliation: Department of Community Dentistry, Institute of Dentistry, University of Oulu, Finland.
authors.forename: Saila
authors.initials: S
authors.lastname: Sutinen
authors.forename: Satu
authors.initials: S
authors.lastname: Lahti
authors.forename: Nigel M
authors.initials: NM
authors.lastname: Nuttall
authors.forename: Anne E
authors.initials: AE
authors.lastname: Sanders
authors.forename: Jimmy G
authors.initials: JG
authors.lastname: Steele
authors.forename: P Finbarr
authors.initials: PF
authors.lastname: Allen
authors.forename: Gary D
authors.initials: GD
authors.lastname: Slade
mesh_terms: D000293:Adolescent; D000328:Adult; D018592:Cross-Over Studies; D003753:Dental Health Surveys; D005387:Finland; D006801:Humans; D008875:Middle Aged; D009909:Oral Health; D011788:Quality of Life; D012107:Research Design; D012647:Self-Assessment; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D013997:Time Factors