Effects of home-based manual dexterity training on cognitive function among older adults: a randomized controlled trial

BACKGROUND: The relationship between manual dexterity and cognitive function among older adults is well known; however, few studies have focused on manual dexterity training that confirms cognitive load of training in older adults through functional near-infrared spectroscopy (fNIRS) and verifies the effect of training. This study examined the effects of home-based manual dexterity training on cognitive function in older adults using a digital trail-making peg test device combining two conventional assessment tools namely, the peg and trail-making tests. METHODS: For 12 weeks, 57 healthy older adults aged 65–88 years participated in a parallel-group, randomized controlled trial, wherein home-based manual dexterity training was performed for approximately 20 min daily. To quantify the cognitive load in different manual dexterity conditions, we assessed the cortical activation patterns of the prefrontal cortex via a wearable four-channel fNIRS device. Participants in the control group were asked to continue their usual daily routines during the intervention period. Cognitive function was assessed using the Stroop Color and Word and Cognitive Impairment Tests. Manual dexterity was assessed using the Purdue Pegboard Test. All outcomes were estimated before and after the intervention. RESULTS: We observed significant differences in prefrontal cortical activation between the different manual dexterity conditions. Only the intervention group showed a significant improvement in Stroop interference (169.0–108.9 ms, p = 0.032) and an executive function and assembly task of the Purdue Pegboard Test (22.5–26.4 counts, p < 0.001). Additionally, except the clock drawing task, cognitive function had a larger effect size (Cohen’s d) in the intervention group (d = 0.26–0.45) than in the control group (d = 0.11–0.28). CONCLUSIONS: Home-based manual dexterity training can improve performance in a complex manual dexterity task and executive functioning in older adults. TRIAL REGISTRATION: UMIN-CTR Clinical Trial, UMIN000047203. Registered 17 March 2022 – Retrospectively registered, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&recptno=R000053844&type=summary&language=E SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s11556-023-00319-2.