Knee pain and future decline in higher-level functional competence in community-dwelling older Japanese: the Kurabuchi cohort study

Background The effect of knee osteoarthritis, which causes knee pain, on higher-level functional competence (HLFC) is not clear. Objective To clarify the effect of knee pain on HLFC in older people. Design Community-based prospective cohort study. Setting Kurabuchi town, Gumma prefecture, Japan. Subjects Community-dwelling individuals aged 65 and older. Methods A total of 808 residents participated to the baseline examinations. The frequency of knee pain, degree of pain and functional impairment resulting from the pain were asked at baseline (2005–2006) via a self-administered questionnaire in Japanese based on an English version of the Western Ontario and McMaster Universities Osteoarthritis Index. Information on HLFC at baseline and during home visits were collected annually until 2014 with the Tokyo Metropolitan Institute of Gerontology Index of Competence. The association between baseline knee pain and HLFC decline was assessed with a Cox proportional hazards model. Results Two factors, persistent knee pain and severe functional impairment caused by the pain, were significantly associated with future declines in total HLFC, with adjusted hazard ratios (95% confidence intervals) of 1.51 (1.08–2.11) and 1.49 (1.10–2.00). In analysis by subcategory, persistent knee pain had a significant adverse effect on participants’ intellectual and social activities, and that severe physical functional impairment also had a significant impact on social activities. Conclusions The clear association of the frequency of knee pain and resultant functional impairment with future HLFC decline indicates that collecting information about these factors may be useful in identifying older people at high risk of future HLFC decline.