Young, but not in the dark—The influence of reduced lighting on gait stability in middle-aged adults

Abstract

Background The aim of this study was to investigate the effects of walking in reduced lighting with or without performing a secondary cognitive task on gait dynamics in middle-aged adults and to compare them with young and old adults. Methods Twenty young (age 28.8±4.1), 20 middle-aged (age 50.2±4.4), and 19 elderly (age 70.7±4.2) subjects participated in the study. Subjects walked on an instrumented treadmill at a self-determined pace under four conditions in randomized order: (1) walking in usual lighting (1000 lumens); (2) walking in near-darkness (5 lumens); (3) walking in usual lighting with a serial-7 subtraction dual-task; and (4) walking in near-darkness with a serial-7 subtraction dual-task. Variability in stride time and variability in the trajectory of the center of pressure in the sagittal and frontal planes (anterior/posterior and lateral variability) were measured. Repeated measures ANOVA and planned comparisons were used to determine the effects of age, lighting conditions, and cognitive task on each gait outcome. Results Under usual lighting, stride time variability and anterior/posterior variability of the middle-aged subjects were similar to those of the young and lower than those of the old. The lateral variability of the middle-aged subjects was higher than that of young adults under both lighting conditions. Similar to the older adults, the middle-aged participants increased their stride time variability when walking in near-darkness, but they were the only ones to exhibit increased lateral variability and anterior/posterior variability in near-darkness. Young adult gait was not affected by lighting, and concurrent performance of a cognitive task while walking did not affect gait stability in all groups under any of the lighting conditions. Conclusions Gait stability decreases in middle age when walking in the dark. Recognition of functional deficits in middle age could promote appropriate interventions to optimize aging and reduce fall risk.

The margin of stability is affected differently when walking under quasi-random treadmill perturbations with or without full visual support

“…Walking in 0.7 lx (full moon on a clear night when walking on a dark street without streetlight) environment increased the variabilities in net center of pressure trajectories ( Chien et al, 2014 ), as well as the area of heel contact distribution within 200 steps ( Ren, Lin & Chien, 2022 ), as compared to walking in 150 lx (the intensity of light in a regular office) in young adults. However, when young adults walked in near-darkness (5 lumens, equivalent to the amount of light output of five candles), no differences were observed in their spatial gait parameter as compared to walking normally (1000 lumens, a bright office, ( Naaman et al, 2023 ). Also, when the environment suddenly became dark for 5 s, the MOSap within this timeframe did not appear to be affected in young adults while walking ( Roeles et al., 2018 ).…”