Methods: The STAR group received usual care; 6 weekly individual face-to-face sessions with the physical therapist for evaluation, graduated therapeutic exercises, and progressive fitness walking; 9 bi-weekly telephone sessions with the nurse for ongoing counseling; and daily physical activity e-diary during intervention for self-monitoring. The attention control group received usual care, and 6 weekly and 9 bi-weekly telephone sessions with the nurse on senior health topics. Knee pain and physical function were measured by the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index. Self-reported daily minutes of participation in fitness walking and daily minutes of performance of lower extremity exercise (repetitions × sets/week) were collected by the e-diary with participation in fitness walking also objectively assessed by daily activity minutes from ActiGraph accelerometers [none to very low (0-99 counts), light (100-2,019 counts), and moderate-to-vigorous (≥ 2,020 counts)] (Dunlop et al., 2011). Systolic and diastolic BP were measured by OMRON BP Monitor. Linear mixed modeling was performed to examine the effect of the STAR intervention vs. attention control on these outcomes over time. Standardized mean differences between the treatment groups (d[between]) for the change from baseline to immediate post-intervention and to six months after the end of the intervention were computed to summarize the observed treatment effects. As changes within the attention control group over time were negligible, standardized mean differences within the STAR group (d[within]) from baseline to immediate post-intervention and to six months after the end of the STAR intervention were also computed.
Results: Participants (N= 182) were on average 65 (SD= 8, range 50-90) years old, 73% (n= 133) female, and 73% (n= 133) white. Significant group by time interactions were found for knee pain (p= 0.015; d[between]= -0.214 at immediate post-intervention; d[between]= -0.183 at six months after the end of the intervention) and physical function (p= 0.016; d[between]= -0.242 at immediate post-intervention; d[between]= -0.208 at six months after the end of the intervention). The STAR group reported having significantly less knee pain and better physical function at immediate post-intervention (d[within]= -0.265 for knee pain; d[within]= -0.293 for physical function) and six months after the end of the intervention (d[within]= -0.194 for knee pain; d[within]= -0.309 for physical function) compared to baseline. Significant group by time interactions were also found by the e-diary for mean daily minutes of fitness walking, mean daily minutes of lower extremity exercise, and mean performance of lower extremity exercise (all p< .0001). Compared to the attention control group, the STAR group had significantly greater improvement at immediate post-intervention and at six months after the end of the intervention in mean daily minutes of fitness walking (d[between]= 0.737 at immediate post-intervention; d[between]= 0.467 at six months after the end of the intervention), mean daily minutes of lower extremity exercise (d[between]= 1.198 at immediate post-intervention; d[between]= 0.819 at six months after the end of the intervention), and mean performance of lower extremity exercise (d[between]= 1.732 at immediate post-intervention; d[between]= 0.812 at six months after the end of the intervention). Compared to baseline, the STAR group reported significantly more mean daily minutes of fitness walking (d[within]= 1.030 at immediate post-intervention; d[within]= 0.621 at six months after the end of the intervention), mean daily minutes of lower extremity exercises (d[within]= 1.110 at immediate post-intervention; d[within]= 0.788 at six months after the end of the intervention), and mean performance of lower extremity exercises (d[within]= 1.592 at immediate post-intervention; d[within]= 0.746 at six months after the end of the intervention). No significant group by time interactions were found by ActiGraph for the three intensity levels (none to very low, light, and moderate-to-vigorous). No significant group by time interactions were found for systolic and diastolic BP.
Conclusion: The STAR intervention had small effects on improvements in self-reported knee pain and physical function at immediate post-intervention that were maintained at six months after the end of the intervention. The treatment effects on pain and physical function were lower than those reported by Fransen et al. (2015) at immediate post-intervention, but similar to those reported by Fransen et al. (2015) at six months after the end of the intervention. Further, the STAR intervention had large effects on improvements in self-reported participation in fitness walking and performance of lower extremity exercise at immediate post-intervention with slight declines at six months after the end of the intervention. However, improvements in objectively assessed fitness walking and BP were not found. Lack of significant group differences in intensity levels by ActiGraph may be due to the slight increase from 3 to 12 mean daily minutes of fitness walking in the STAR group. Mean daily minutes of lower extremity exercise increased from 1 to 9 in the STAR group, but is not detectable by ActiGraph. While fitness walking reportedly increased, the mean fell short of the goal of 21 mean daily minutes (150 minutes/week), which may have contributed to lack of difference in BP. Enhancements to the STAR intervention, such as addition of significant other support, may further improve outcomes.
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