Patterns of discordance of physical functioning in older persons; different associations for apathy and depression? Results from the NESDO-study

Objectives Discordance between self-reported functional limitations and performance-based physical functioning may have a negative impact in functional independence in older adults. We longitudinally examined baseline apathy- and depressive symptomatology as associates of discordance. Method 469 participants from the multi-site cohort study NESDO were included. Self-reported functional limitations were assessed by two items derived from the WHO-Disability Assessment Schedule. Performance-based physical functioning included walking speed and handgrip-strength. Both measures were rescaled, with final sum-scores ranging from 0 to 6. Discordance-scores were computed by subtracting sum-scores on performance-based measures from self-reported functional limitations. Using latent growth curve analysis, we estimated individual trajectories of discordance at baseline, 2-and 6-years follow-up, consisting of the baseline discordance-score (intercept) and the yearly change of discordance-score (slope). We then estimated associations with apathy and depression indicators. Results At baseline, persons (mean age 70.48 years, 65% female, 73% depressed) on average overestimated their daily functioning compared to performance tests (b = 0.77, p < 0.001). The average discordance-scores yearly increased by 0.15 (p < 0.001). Only in models adjusted for several demographic and clinical characteristics, depression severity was negatively associated with discordance-scores at baseline (b=-0.01, p = 0.02), while apathy was not (b=-0.02, p = 0.21). No associations with change over time were found. Conclusion In older persons, not indifference and diminished goal-directed activity, but negative emotions appear to underlie underestimation of one's physical capacity. Further research is needed to determine (1) to what extent targeting discordance results in actual preservation of physical functioning and (2) whether older persons with apathy and/or depression need different approaches for this purpose.