Cognitive decline is a major public health care issue and a well-recognized clinical manifestation of cognitive decline are falls. Seniors with cognitive impairment fall at twice the rate of peers without cognitive impairment 1, 2.
Exercise training may be an effective strategy against cognitive decline 3–6 and it is recommended for prevention of falls. We recently reported that 12 months of once-weekly (1x RT) or twice-weekly resistance training (2x RT) improved selective attention and conflict resolution compared with a balance and tone program (BAT; control) among 155 community-dwelling senior women (i.e., Brain Power study; NCT00426881) 4. We also found that both resistance training programs provided better value for falls prevented compared with the BAT (control) program {Davis, 2010 #336}. As no study has examined whether benefits of exercise persist after formal cessation of an intervention, we examined whether improved selective attention and conflict resolution as well as economic benefits were sustained 12 months after formal cessation the Brain Power resistance training study.
METHODS
We conducted a 12-month follow-up study from May 2008 to April 2009. Of the original 155 participants, 123 consented to the follow-up study. Ethical approval was obtained from the Vancouver Coastal Health Research Institute and the University of British Columbia’s Clinical Research Ethics Board.
Our primary outcome measure was the specific executive cognitive function of selective attention and conflict resolution, as measured by the Stroop Test 8. Secondary measures included set shifting, working memory, and current physical activity level.
Between-group differences in executive cognitive functions were compared by multiple linear regression analyses as in our original trial 4. For current physical activity level, baseline score and experimental group were used as covariates. Two planned simple contrasts were performed to assess differences between: 1) the 1x RT group and the BAT group; and 2) the 2x RT group and the BAT group. The overall alpha was set at p<0.05.
For the economic evaluation, we calculated the incremental cost per fall prevented for both 1x RT and 2x RT compared with BAT from a Canadian Health Care System perspective using a 21-month time horizon (2009 prices). All hospital admission related costs were based on a fully allocated cost model of a tertiary care hospital or the British Columbia Medical Services Plan 2009 price list.
RESULTS
Of the 123 who consented, 109 completed the assessment at the end of the 12-month follow-up; 37 from the 1x RT group, 41 from the 2x RT group, and 31 from the BAT group. The mean (SD) age of the cohort was 71.6 (3.0) years.
There was a significant between-group difference in selective attention and conflict resolution at the end of the 12-month follow-up study (p=0.04). Specifically, the 1x RT group sustained improved Stroop performance compared with the BAT group (p=0.04). There were no significant between-group differences in set shifting, working memory, and current physical activity level.
The unadjusted incidence rate ratio over the 2-year period for the 1x RT group indicated a 30% (IRR: 0.70, CI: 0.37–1.33) non-significant reduction in falls and an 8% (IRR 1.08: CI: 0.79–1.47) non-significant increase in the 2x RT group.
Based on the point estimates from our base case analysis we found that the 1x RT group incurred fewer health care resource utilization costs and had fewer falls than the BAT group; thus 1x RT was less costly and more effective than BAT (i.e., 1x RT dominates BAT). Although the 2x RT group also incurred fewer care utilization costs than BAT, the 2x RT group suffered more falls. Thus, 2x RT was less effective than BAT.
COMMENT
We provide novel data suggesting that both the cognitive and economic benefits of once-weekly resistance training can be sustained 12 months after its formal cessation. Specifically, 12 months after trial completion, former participants of the 1x RT group demonstrated a 15% improvement in their performance on the Stroop Test compared with those in the BAT group. This novel finding strengthens the emerging belief that targeted exercise training may combat age-related decreases in cognitive function. Further, there was a significant reduction in health care resource utilization costs of falls 12 months after trial completion for the 1x RT and the 2x RT compared with BAT (control). Thus, cognitive and economic benefits of participating in a 12-month resistance training intervention were sustained for the 1x RT while these benefits were not sustained for the 2x RT. The 1x RT group demonstrated a 5% increase (NS) in current physical activity level from baseline compared with a 6.6% reduction (NS) in the 2x RT group. Hence, maintaining physical activity level may be essential in sustaining the benefits of resistance training. Such findings should remain guarded as future studies investigate factors that explain this observed variation in exercise-induced cognitive benefits in terms of costs and consequences.
Table 1.
Mean values (SDs) for outcome measures and results of base case analysis for economic evaluation
| Outcome Measures | BAT | 1x RT | 2x RT |
|---|---|---|---|
| Baseline (N=155) | Mean (SD) | Mean (SD) | Mean (SD) |
| Stroop CW – Stroop C (sec) a | 43.98 (15.1) | 47.37 (26.2) | 45.02 (15.8) |
| Trail B – Trail A (sec) | 47.12 (41.3) | 41.35 (26.5) | 49.53 (36.6) |
| Digit Forward – Digit Backward | 3.2 (2) | 3.5 (2) | 3.4 (2) |
| Physical Activity Scale for the Elderly | 126 (51) | 116 (61) | 121 (60) |
| 12-Month Follow-Up (N=109) | Mean (SD) | Mean (SD) | Mean (SD) |
| Stroop CW – Stroop C (sec) | 44.84 (15.8) | 39.62 (16.6) b | 45.51 (27.4) |
| Trail B – Trail A (sec) | 39.51 (26.8) | 32.45 (39.0) | 43.97 (37.8) |
| Digit Forward – Digit Backward | 3.3 (2) | 3.3 (2) | 2.7 (2) |
| Physical Activity Scale for the Elderly | 134 (57) | 122 (61) | 113 (57) |
| Base Case Analysis for Economic Evaluation | |||
| Number of falls per year over 9 months c | 38 | 30 | 38 |
| Number of falls per year over 12-month follow-up study | 20 | 17 | 37 |
| Total number of falls over 21-months | 58 | 47 | 65 |
| Incremental number of falls prevented over 21-months | reference | 11 | -7 |
| Incremental cost (total health resource utilization) | reference | -$1857 b | -$1077 b |
Stroop CW = Stroop colour-words condition; Stroop C = Stroop coloured-X’s condition.
Significantly different from the BAT group at p<0.05.
Total number of falls for 9-months of the 12-month randomized controlled trial.
Acknowledgments
The authors would like to thank the Vancouver South Slope YMCA management and members who enthusiastically supported the study by allowing access to participants for the training intervention. We thank the instructors for their commitment to the participants’ health and safety.
Drs. Liu-Ambrose, Marra, and Handy are Michael Smith Foundation for Health Research Scholars. Dr. Marra is a Canada Research Chair in Pharmaceutical Outcomes. JCD is a Canadian Institutes for Health Research Canada Graduate Scholarship PhD trainee.
Funding: The Vancouver Foundation (BCMSF, Operating Grant to TLA) and the MSFHR (Establishment Grant to TLA) provided funding for this study. The Canada Foundation for Innovation funded essential infrastructure used in this study (New Opportunities Fund to TLA).
Footnotes
Data from this manuscript were presented at the following scientific meetings:
Not applicable.
Trial Registration: ClinicalTrials.gov Identifier: NCT00426881
Data Access and Responsibility: TLA and JCD had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Author Contributions:
TLA, JCD, CAM: Study concept and design, acquisition of data, analysis and interpretation of data, preparation of manuscript, and critical review of manuscript. MN, MCR, LSN: Acquisition of data, analysis and interpretation of data, preparation of manuscript, and critical review of manuscript. PG, BLB: Study concept and design, acquisition of data, interpretation of data, and critical review of manuscript.
All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis.
Sponsor’s Role: None.
Conflict of Interest: All authors have nothing to declare.
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