Synergistic effects of exercise, cognitive training and vitamin D on gait performance and falls in mild cognitive impairment—secondary outcomes from the SYNERGIC trial

Background Older adults with mild cognitive impairment (MCI) have a higher risk of gait impairments and falls; yet, the effects of multimodal interventions, including combinations of exercises with cognitive training, on improving their mobility remain unclear. Objectives To investigate the synergistic effects of aerobic-resistance exercise combined with cognitive training, with or without vitamin D supplementation, on gait performance and falls risk in older adults with MCI. Methods The effect of 20 weeks of aerobic-resistance exercise, cognitive training, and Vitamin D supplementation (10 000 IU 3×/week) on gait and falls in older adults with MCI was evaluated in the SYNERGIC trial, using a fractional factorial design. Assessments were conducted at baseline, 6-month endpoint (after intervention) and 12-month endpoint (follow-up). Eligible participants were between the ages of 65 and 84 years with MCI enrolled from 19 September 2016 to 7 April 2020. Main outcomes of interest for gait performance were gait speed and gait variability changes, whilst for falls were incidental falls and incidental injurious falls. Results Amongst 161 participants, the four exercise-based arms improved gait speed (+7.5 cm/s, P < .001) and reduced falls (incidence rate ratios (IRR) = 0.65, 95% confidence interval (CI): 0.32–1.42, P = .25) and injurious falls (IRR = 0.38, 95% CI: 0.15–1.05, P = .05) at 6-month endpoint. Falls reduction reached statistical significance (IRR = 0.28, 95% CI: 0.13–0.64, P = .002) at 12-month endpoint. Exercises combined with cognitive training showed the greatest gains in gait speed at 6-month endpoint (P < .001) and in reducing falls at 12-month endpoint (IRR = 0.24, 95% CI: 0.05–0.77, P = .02) compared to the control. Vitamin D did not enhance outcomes and increased gait variability, a marker of instability. Conclusion Aerobic-resistance exercise combined with sequential computerised cognitive training improved gait performance at 6 months and decreased the risk of falls and injuries at 12 months in older adults with MCI. The addition of vitamin D did not produce benefits.