Study design

This study was a randomized controlled trial testing the effect of home-based CCT using SoroTouch. As this is our first clinical trial of this application, we selected the office of the Niyokatsu general incorporated association for the place to collect the primary outcome data which helped us recruit the study participants and let us use their space. Due to the availability of the human resource and physical space, the number of the participants was set as 20. With this sample size, a two-tailed test at a significance level of 0.05 can detect an effect size of 1.4 with a power of 0.8. The participants were assigned randomly to the intervention (SoroTouch) group or control group using the Mujinwari cloud service (https://mujinwari.biz/users/login). The SoroTouch group were asked to engage in cognitive training using SoroTouch every day for 6 months at home, while the control group did not receive any specific intervention. In order to investigate the effect of the intervention, all participants were administered tests of cognitive functions: CogEvo (Total Brain Care, Kobe, Japan) in the office of the Niyokatsu general incorporated association and the Japanese version of the Montreal Cognitive Assessment (MoCA-J) [20] at a certain internist clinic, before and after the intervention. CogEvo was also administered to all participants once per month during the 6-month intervention period. In addition to these tests, before and after the intervention, the participants were also asked to fill in the 36-Item Short-Form Health Survey [21], a questionnaire measuring health-related quality of life, whose results are not reported in this paper since quality of life was not the focus of this study. The study design is illustrated in Fig 1. The intervention started in November 2021 and was completed in May 2022.

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Fig 1. Study design.

https://doi.org/10.1371/journal.pone.0299201.g001

This study was approved by the Ethics Committee of Showa University on August 25, 2021. (Approval No. S7). All participants provided written informed consent prior to the administration of the first cognitive functions test, and received compensation of 5,000 yen per month for their participation, regardless of the assigned group. This study has been registered in the Japan Registry of Clinical Trials (JRCT), with the trial ID, jRCTs032210356.

Participants

The participants of this study were 20 individuals (6 men, 14 women) aged 42–79 years who were recruited from the participants of community-based activities for reducing the risk of dementia held by the Niyokatsu general incorporated association. The age range of the participants was selected for the following reasons; (1) In Japan, people aged 40 and over are legally insured by long-term care insurance, and have easier access to medical services for prevention of health problems, compared to younger people [22]. (2) A majority of individuals over 80 years old do not often use a computer or the internet, which prevents them from using the software without assistance [23]. The inclusion criteria were as follows: 1) age 40–79 years; and 2) willing to use SoroTouch for a period of 6 months. Individuals who met any of the following conditions were excluded: 1) diagnosed with dementia or mild cognitive impairment (MCI); and 2) unable to come to the office of the general incorporated association alone. The participants’ demographic and clinical characteristics that are associated with the risk factors for dementia are shown in Table 1. This information was collected following the procedure presented by Livingston et al. [24].

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Table 1. Participants’ demographic and clinical characteristics and their group comparison.

https://doi.org/10.1371/journal.pone.0299201.t001

SoroTouch

SoroTouch (Fig 2) is an application software for tablet devices that trains individuals to acquire mental manipulation skills using a Japanese abacus, and it was originally developed for educational purposes. On this software, the user performs calculation exercises, such as 8 + 1 − 7 + 2 + 5 and 29 + 13 + 57, by touching and swiping ovals that resemble abacus beads on the screen, as well as by mental calculation. SoroTouch has an instructional section that teaches participants how to perform calculations using the abacus. The task difficulty changes depending on the percentage of items answered correctly, but can also be controlled by the users themselves.

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Fig 2. SoroTouch.

(A) Display screen of SoroTouch. (B) A participant using SoroTouch.

https://doi.org/10.1371/journal.pone.0299201.g002

CogEvo

CogEvo is a test battery of cognitive functions that assesses the function of various kinds of cognitive domains (visuospatial abilities, orientation, working memory, attention, planning, et al) through the performance of 12 cognitive tasks on a tablet device with a touch panel. In this study, we used the following five core tasks for measurement of the intervention outcomes (S1–S5 Files).

1. Same shape; The examinees are asked to select the same figure as the one displayed in the center of the panel from among six figures placed at different angles around (S1 File). The raw score of this task was found to be positively correlated with the score of Design copying in MMSE (r = 0.23, p<0.05) that reflects one’s visuospatial abilities, in subjects of early stages of Alzheimer’s Disease (AD) [25].
2. Orientation; This task requires the examinees to select the correct day, week and time of the examination day, and the 1–2 days before and after that day (S2 File). The performance of this task was positively correlated with the score of Temporal orientations in MMSE (r = 0.76, p<0.01) in subjects of early stages of AD [25].
3. Flashing light; The examinees are asked to remember the order in which the four colors of red, blue, green and yellow lights glow, and then, touch the lights in the same order. The score is calculated based on accuracy (S3 File). The score of this task was associated with the scores of Serial 7’s of MMSE (r = 0.39, p<0.01) that reflects working memory in subjects of early stages of AD [25].
4. Route 99; The examinees are requested to trace squares on the panel from the starting point to the goal so that they pass randomly displayed digits in order from 1 to 10 (S4 File). This task requires arrangements to reach the goal quickly and measures planning that is one of the subdomains in executive functions [26]. The score of this task is known to be related to the scores of Serial 7’s of MMSE (r = 0.43, p<0.01) that assesses one’s working memory in subjects of early stages of AD [25].
5. Follow the order; This task is one version of Trail Making Test, which is one of the most frequently used neuropsychological tests that measures attention, specifically, an ability to sustain attention and an ability to shift attention [27–29]. On this task, the examinees are asked to touch the symbols displayed in the panel in a designated order. The type of symbols are numbers (1, 2, 3…), Japanese hiragana, and alphabet characters (A, B, C…), depending on the trial. In one trial, the examinee is asked to touch the numbers and alphabets alternatively (1, A, 2, B, 3, C…) (S5 File). The score of this task was positively correlated with the score of Serial 7’s of MMSE (p = 0.41, p<0.01) in subjects of early stages of AD [25].

Sawada et al [30] previously demonstrated the validity and reliability of CogEvo and S. Ichii et al [31] reported that the tool can be used to evaluate age-related or pathological decline in cognitive functioning.

MoCA-J

MoCA-J is a brief and useful face-to-face cognitive screening tool for MCI [20]. MoCA-J assesses abilities in the following eight cognitive domains: visuospatial abilities/executive functions, naming, attention, language, abstraction, delayed recall, and orientation. Naming, abstraction, delayed recall, and orientation are measured using a single task, and visuospatial abilities/executive functions, attention, and language are assessed according to performance in multiple tasks. Visuospatial abilities/executive functions are measured using the alternating trail making B, 3-D cube copy, and clock drawing tasks. Attention is measured using the digits forward and backward, vigilance sustained attention, and serial subtraction tasks. Language is assessed according to performance in the repetition and verbal fluency tasks. The total score of MoCA-J ranges from 0 to 30, and a cut-off score of 25/26 is used as an indicator of MCI. MoCA-J has shown high reliability and validity [20, 32].

Intervention

The participants in the SoroTouch group were asked to use SoroTouch for 30 min every day for a period of 6 months at home. The status of the participants’ usage (time they used the software for) and performance (whether they answered each item correctly) was monitored online by the staff of the general incorporated association. At the beginning of the intervention period, the participants in the SoroTouch group were provided a tablet device with SoroTouch installed and instructions on how to use the software in a face-to-face setting. Since one of the participants did not understand fully the initial instructions, she was provided with additional instructions via telephone approximately twice a month throughout the intervention period. At 1 month after the intervention started, one participant was found to use SoroTouch on only 13 days in the first month. Therefore, he received a phone call for encouragement twice a month so that he would use the software more frequently; however, he continued to use SoroTouch for only approximately 10 days a month. The participants in the control group did not receive any specific cognitive training or other specific interventions.

Data analysis

The primary outcomes were the total score and scores on each task of the CogEvo. Secondary outcomes included total scores and scores on each subcategory of the MoCA-J. To investigate the effect of SoroTouch, the participants’ characteristics and scores for CogEvo and MoCA-J were compared between the SoroTouch and control groups. Because there were 6 primary outcomes and each was observed at six-time points, a Bonferroni correction was applied for our hypothesis testing. As a result, the adjusted criterion for statistical significance of the primary outcomes was 0.0014, and p-values smaller than this threshold were considered significant. The descriptive statistics were reported using means and standard deviation (SD) for continuous variables. To analyze the effect of the intervention on the total scores and scores on each task of CogEvo, mixed effect models for repeated measures were applied. We had planned to use analysis of covariance, but we changed it to analyze repeated measures data before fixing clinical trial data. For the analyses, the baseline scores, groups (SoroTouch or control), timing of examination, and interaction between groups and timing of examination were set as covariates. To examine the effects of the intervention on the scores of MoCA-J, analysis of covariance was conducted, setting the baseline scores as covariates. We had planned to use an unpaired t-test, but we changed it to adjust for the baseline score. All statistical analyses were conducted using SPSS Statistics 28 (SPSS, Inc., Chicago, IL, USA).

Study limitations

This study has several limitations that merit consideration. First, the participants were not followed-up after the intervention period was over; therefore, no information was obtained about how long the effect of the intervention lasted for. Second, the present study had 10 participants each in the control and SoroTouch groups, and the small sample size resulted in low power. Third, all participants were healthy and recruited from a group engaging in community activities provided by a specific organization. We aimed to adapt home-based cognitive training with the SoroTouch for use in the general community, specifically for older individuals who are cognitively healthy, so we consider our findings are applicable to a broader population. However, further trials are needed to investigate the effectiveness of home-based CCT with the SoroTouch for people at risk of MCI and cognitive impairment. Hence, larger and longer studies should be planned with more diverse participants including who have already started to develop dementia or MCI. Lastly, we were unable to confirm the identity of the actual users of SoroTouch, like other home-based online activities without a video, though we were able to track the exact timing of each participant’s usage daily as they used SoroTouch online. To address these limitations, regular follow-up sessions, either in person or online, should be included in the protocol for future trials.