Association between chronotype and dual-task gait cost across distinct cognitive domains in healthy young adults.

Serial subtraction by seven (SS7) produced the largest mean velocity dual-task cost compared to the other two cognitive conditions.

• SS7 produced a mean velocity DTC of -12.76%
• This was significantly greater than backward word spelling (5LWB) at -7.95% (p = 0.002)
• SS7 was also significantly greater than reverse month recitation (RMR) at -9.57% (p = 0.021)
• Condition differences were assessed with nonparametric tests and post-hoc comparisons

MEQ score independently predicted mean velocity dual-task gait cost during backward word spelling (phonological task).

• β = -0.51, p < 0.001, R² = 0.269 in the multiple linear regression model
• Greater morningness (higher MEQ score) was associated with better gait-speed preservation under cognitive load
• The model adjusted for age, sex, BMI, and baseline gait velocity
• Sample consisted of 69 healthy young adults with mean age 21.3 years

MEQ score independently predicted mean velocity dual-task gait cost during reverse month recitation (sequential task).

• β = -0.55, p = 0.004, R² = 0.222 in the multiple linear regression model
• Greater morningness was associated with better gait-speed preservation under this sequential cognitive load
• The model adjusted for age, sex, BMI, and baseline gait velocity
• The association was statistically significant unlike that for SS7

MEQ score did not significantly predict mean velocity dual-task gait cost during serial subtraction by seven (arithmetic task).

• β = -0.33, p = 0.071 in the multiple linear regression model
• Despite SS7 producing the largest gait interference overall, the chronotype association was the weakest for this condition
• The authors suggest 'arithmetic dual-task disruption may be less sensitive to circadian arousal'
• The model was adjusted for age, sex, BMI, and baseline gait velocity

Exploratory Spearman correlations showed MEQ-DTC associations were broadest in the phonological task and narrowest in the arithmetic task across gait parameters.

• MEQ-DTC associations were found across 7 of 8 gait parameters in the 5LWB (phonological) condition
• Associations were present in 4 of 8 parameters in the RMR (sequential) condition
• Associations were present in only 3 of 8 parameters in the SS7 (arithmetic) condition
• Eight spatiotemporal gait parameters were examined in total using three-dimensional motion capture

The study sample consisted of 69 healthy young adults assessed with standardized chronotype and gait measurement tools.

• 37 of 69 participants were female; mean age was 21.3 years
• Chronotype was measured using the Morningness-Eveningness Questionnaire (MEQ)
• Spatiotemporal gait parameters were recorded with three-dimensional motion capture
• Three dual-task conditions were used: backward word spelling (5LWB), serial subtraction by seven (SS7), and reverse month recitation (RMR)
• DTC was calculated for eight gait parameters

The authors identify fixed testing time and cross-sectional design as key limitations that could conflate chronotype effects with time-of-day confounds.

• All participants were tested at a single fixed time point, preventing separation of chronotype from time-of-day effects
• The cross-sectional design precludes causal inference
• The authors call for 'within-subject, multi-timepoint studies to confirm chronotype effects separate from time-of-day confounds'
• These limitations apply to interpretation of all regression and correlation findings