Gradual cognitive decline is nearly universal and is well recognised as a normal part of the ageing process. According to Salthouse,38
most age-related cognitive deteriorations are at least partially attributable to declines in information processing speed, which affects episodic and working memory, verbal fluency and reasoning abilities. Previous work, especially the US NIH-funded multisite ACTIVE trial, has led to the development of a promising, second-generation computer-based intervention to improve visual processing speed known as Road Tour. We designed the IHAMS to assess the efficacy and effectiveness of Road Tour.
There are five important aspects of IHAMS that warrant further mention. First, the IHAMS overcomes five major limitations of the previous US NIH-funded ACTIVE multisite RCT, the first three of which we were able to directly evaluate in this article reporting on the post-training results. In addition to participants aged 65 years or older, the IHAMS included 50–64-year-olds to determine whether speed of processing training is efficacious and effective before substantial cognitive decline occurs in the seventh decade.39
If speed of processing training is efficacious in this younger cohort, preventive interventions could focus on improving cognitive functioning before the rapid age-related declination process even begins. The IHAMS also used an attention control group that was trained on computerised crossword puzzles rather than a no-contact control group. This allowed us to directly evaluate the potential that placebo effects cloud the interpretation of the results from ACTIVE.25
By using Road Tour rather than its predecessor, the IHAMS avoids reliance on a supervised training intervention. This allowed us to directly evaluate whether sending participants home with the software to use on their own PCs is efficacious, and if so, whether it was as effective as supervised on-site training, which potentially expands substantially the ability to implement widespread public health interventions. The IHAMS also directly randomised participants to receive or not receive on-site booster training, as opposed to the adherence-conditioned assignment to booster training used in ACTIVE. When the 1-year follow-up data become available, this will allow us to separate the effects associated with standard dosing from those derived from standard dosing plus booster training. The IHAMS also included five additional neuropsychological tests assessed at baseline that will also be assessed at the 1-year follow-up as secondary outcomes. Once the 1-year follow-up data become available, this will allow us to assess the extent to which Road Tour effects on the primary outcome transfer to the other cognitive functions tapped by these neuropsychological tests.
The second important aspect of this study involves the training intervention itself. Road Tour is easy to use on any PC (versions for both PC and Apple platforms are available) at any location. Adherence to training was very good, even in the at-home training group, which did not benefit from the support of weekly scheduling contacts. The targeted standard training dose was just 10 h, although the mean amount of time that it was used in the two on-site training groups was only 7.8 h spread over a 5-week period. The 2 h training sessions were extremely well tolerated, and no discomfort of any kind was reported by any participant during delivery of the standard training dose. In sum, the ability to readily implement Road Tour training in widespread public health interventions is extremely promising from a logistical perspective.
The demonstrated efficacy of Road Tour to improve UFOV scores in these interim analyses is the third important aspect of this study that warrants further mention. Three different analytic approaches—multiple linear regression, general linear mixed effects and multiple logistic regression models—all substantially supported our hypothesis for the post-training effects in all respects. The primary analytic approach was the pooled multiple linear regression of the Blom rank transformed UFOV composite at post-training. When these analyses were done pooling both age strata, the regression coefficient for random assignment to any Road Tour training group versus the attention control group was statistically significant (p<0.001) with an effect size of −0.558 (adjusted for the Blom rank transformed UFOV test at randomisation). Similar results were also obtained when comparing each of the three training groups with the attention control group. That this medium effect size was obtained with an average of <8 h of training suggests that the potential for widespread public health interventions is very promising.
Directly comparing the efficacy of Road Tour obtained in these IHAMS interim analyses to the speed of processing training results obtained from a meta-analysis consisting of ACTIVE and five other visual speed of processing training RCTs with a total enrolment of 907 subjects followed for varying time lengths13
is problematic for at least four reasons. First, most of those RCTs used the touch screen version of the UFOV, which has four subtests and yields a composite score that ranges between 68 and 2000 ms, while IHAMS used the PC mouse version, which has only three subtests and yields a composite score that ranges between 51 and 1500 ms. Second, most of those RCTs used a no-contact control group design that added any potential placebo effect to their training effect estimates. Moreover, IHAMS used an attention control group that was trained using a computerised crossword puzzle programme that may have led to some improvement in processing speed beyond the potential placebo effect. Third, all those RCTs used the predecessor version of the speed of processing software that required supervised on-site training. Fourth, IHAMS used less robust mental status and self-reported visual acuity screening tools than those RCTs for exclusion purposes, which enhances the generalisability of the IHAMS while biasing its effect size estimates towards the null. Taking the four differences noted above into consideration, the effect sizes for those six RCTs are quite comparable to the post-training effect size estimated from our multiple linear regression model of −0.56 and from our general linear mixed effects model of −0.43.
The fourth important aspect of this study that warrants further mention involves the comparison of the on-site versus the at-home training effects in these interim analyses. For the two on-site Road Tour training groups, the effect size estimates from the multiple linear regression model were −0.457 and −0.585, while the effect size estimate for the at-home training group was −0.629. Thus, the effect size was largest for the at-home training group, although all three estimates are within the others' 95% CIs, reflecting their comparability. Therefore, the benefits that accrue from Road Tour training can be achieved using a home PC without supervision, which substantially increases the opportunity to implement speed of processing training in widespread public health interventions.
The final aspect of this study that warrants further mention involves the efficacy equivalence between the two age strata in these interim analyses. Among older adults (≥65 years old), the estimated effect size from the multiple linear regression analysis was −0.479, while it was −0.626 among younger adults (50–64 years old). Moreover, when an interaction term was added to the model in the pooled analysis, no statistical difference in these estimates was observed. This finding of equivalence in the efficacy of Road Tour between the age strata is extremely promising because it suggests that preventive interventions could focus on improving cognitive functioning at an earlier stage of age-related decline.
In conclusion, we note that although our study has numerous strengths, it does have limitations, four of which are worth mentioning. First, although large, the sample was drawn from just one FCC in which minorities were under-represented. Second, to be eligible, participants had to have a home computer and internet access. Third, only one of the five training programmes included in Posit Science's Insight suite (Road Tour) was studied. Finally, only data on the primary outcome were available and then only at randomisation and post-training. The first two of these limitations constrain the generalisability of the IHAMS somewhat, while the last two leave the issues of potential benefits from multifaceted training (using all five of the training programmes in the Insight suite) and the transferability to the five other neuropsychological outcomes unresolved.