TOPLINE:

Researchers identified four distinct within-day patterns of physical activity in adults with or at high risk for knee osteoarthritis (OA). Being less active in the morning and evening was linked to an approximately twofold increased risk for all-cause mortality.

METHODOLOGY:

• Researchers conducted a secondary analysis of data from an observational study to examine whether patterns of physical activity within a day were associated with risk for mortality in adults with or at risk for knee OA.
• They included 1927 participants (mean age, 65.1 years; 55.3% women) from four clinical sites in the US.
• Participants wore a hip accelerometer during waking hours for 7 days. Analyses used data from at least 4 valid days, converted minute-by-minute data into hourly totals, checked for nonwear time, and calculated minutes of moderate-to-vigorous activity.
• Researchers identified within-day activity patterns and grouped participants into tertiles of low, middle, or high expression of each pattern. The middle tertile was considered the reference group.
• The primary outcome was all‑cause mortality assessed over up to 8 years. Analyses were also stratified by weekly moderate‑to‑vigorous activity levels (< 30 vs ≥ 30 minutes).

TAKEAWAY:

• The analysis identified four within-day activity patterns that explained about 82% of the variation in the physical activity of the sample: high overall activity, high evening activity, high morning and evening activity, and very high morning activity.
• Participants in the lowest tertile of the high morning and evening activity pattern had about double the risk for mortality than those in the middle tertile (adjusted hazard ratio [aHR], 2.09; 95% CI, 1.15-3.80). The risk for mortality was 1.78 times higher in those in the lowest vs middle tertile of the high evening activity pattern (aHR, 1.78; 95% CI, 1.01-3.12).
• Among participants with less than 30 minutes per week of moderate-to-vigorous activity, those in the lowest tertiles for high morning and evening activity and very high morning activity had increased risks for mortality (aHR, 3.74 and 2.48, respectively).
• Survival over 8 years was 98% in the highest tertiles, 97% in the middle tertiles, and 93% in the lowest tertiles across all four patterns.

IN PRACTICE:

“Since most adults with knee OA do not meet minimum activity guidelines, within-day patterns may be useful to identify activity limitations not reflected by overall volume of activity. These patterns could serve as a clinical marker indicating an impairment in patients otherwise reporting low symptom burden,” the authors of the study wrote.

SOURCE:

This study was led by Sydney C. Liles, PT, DPT, MS, University of Delaware in Newark, Delaware. It was published online on December 22, 2025, in Arthritis Care & Research.

LIMITATIONS:

The sample comprised mostly well-educated White women, which limited generalizability. Researchers replaced nonwear hours with sample averages, which may have biased activity patterns. The 8-year follow-up and high survival may have limited the power to detect associations.

DISCLOSURES:

This study received support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institutes of Health, the Rheumatology Research Foundation, and the Arthritis Foundation. The authors did not report any conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.