Author(s): VAN ROIE, E., DELECLUSE, C., LÖPPÖNEN, A., Institution: UHASSELT, Country: BELGIUM, Abstract-ID: 1255

INTRODUCTION:
Stair walking ranks among the most difficult daily activities with advancing age, making it a valuable indicator of functional status. While lab-based assessments using sensor-based technologies have enabled detailed assessments of stair-walking capacity, such assessments require standardized testing in controlled settings, limiting scalability and frequent monitoring. Recent advances in thigh-worn wearables have enabled new opportunities to examine this behavior in the free-living environment. Therefore, this study aims at investigating (1) the effect of age and sex on free-living stair-walking metrics, and (2) the associations between free-living stair-walking metrics and lab-based physical capacity in middle-aged to older adults.
METHODS:
Ninety-nine participants (45-64 years: 19 males, 30 females; 65-84 years: 25 males, 25 females) performed the following lab-based physical capacity tests: handgrip strength, 10-m fast walk, 6-minute walk test, timed up-and-go, 5-repetition sit-to-stand, and 6-step stair ascent. In addition, they wore a tri-axial accelerometer (100Hz, UKK RM42) on the dominant thigh for 3 to 7 consecutive days. Stair-walking bouts in free-living conditions were detected from raw accelerometer data using ActiPASS software. Both the number of bouts and the total stair-walking duration per day were calculated. Mean amplitude deviation (MAD) in 2-second epoch was used to estimate the intensity of each bout. Two-way analyses of covariance examined the main effects of age group and sex, as well as their interaction, on free-living stair-walking metrics, while controlling for body mass index (BMI). Associations between free-living stair-walking metrics and lab-based physical capacity were examined using Pearson’s correlation coefficients.
RESULTS:
A main effect of BMI was noted for the average number of stair-walking bouts per day (F(1, 94) = 6.32, p = 0.014), indicating more bouts/day with decreasing BMI. Neither the duration nor the number of bouts per day showed an effect of age or sex. Middle-aged demonstrated higher MAD intensities compared to older adults (F(1, 94) = 9.62, p = 0.003). A tendency towards lower MAD intensities was shown in females versus males (F(1, 94) = 3.54, p = 0.063), and these differences increased with age, as demonstrated by a significant age group by sex interaction effect (F(1, 94) = 4.51, p = 0.036). MAD intensity values were associated with all physical capacity tests (|r| = 0.246-0.468; p < 0.05), while no associations were found for stair-walking duration or number of bouts per day (all p > 0.05).
CONCLUSION:
Free-living stair-walking intensity was lower in older compared to middle-aged adults and showed consistent associations with validated lab-based physical capacity tests. These findings support the potential of free-living stair-walking intensity as scalable, digital biomarker of functional status in aging populations.