Effect of physical activity on cognitive function in older adults at risk for Alzheimer disease: a randomized trial
Lautenschlager NT, Cox KL, Flicker L, Foster JK, van Bockxmeer FM, Xiao J, Greenop KR, et al.;
Commented by , 12 Sep 2008
Aim of the study
To determine whether physical activity reduces the rate of cognitive decline in older adults at risk.
Methods
In this "Fitness for the Aged Brain Study" run in a single site in Perth, Australia, 301 potential participants over age 50 reporting memory problems were screened for eligibility using the Telephone Interview for Cognitive Status-modified and the Geriatric Depression Scale.
After an in-person further assessment to rule out dementia and inability to walk for 6 minutes without assistance, 170 were randomized to an education & usual care group or to a 24-week home-based program of moderate-intensity at least 150 minutes per week over 3 sessions.
The main outcome measure was change in Alzheimer Disease Assessment Scale – cognitive subscale (ADAS-cog) scores over 18 months. Secondary outcomes included word list immediate and delayed recall, Clinical Dementia Rating sum of boxes, digit symbol coding, verbal fluency, Beck depression scale, Medical Outcomes Short-Form, Community Healthy Activities Program for Seniors, apoE genotype.
Results
138 completed the 18-month assessment. In the intent-to-treat (ITT) analysis, participants in the physical activity group improved their ADAS-cog score 0.26 points (95% CI, -0.89 to 0.54) whereas the usual care group deteriorated 1.04 (95% CI, 0.32 to 1.82) at 6 months (end of intervention).
After 18 months the changes in ADAS-cog scores were 0.73 and 0.04 respectively (p = 0.04) using ANCOVA for repeated measures between participants. World list delayed recall was also statistically significant (p = 0.02) in favor of physical exercises. Non-carriers of apoE4 had better ADAS-cog scores.
Professor Gauthier's comments
This study is important in many respects. The methods used (randomized allocation to either of two treatment arms, standardized cognitive measures, ITT analysis, genotyping) for this non-pharmacological intervention are at par with traditional drug studies. The effect on cognition was detected at the end of the intervention (6 months) and still present a year later, with a good retention (138/170) rate.
The mechanisms for this effect are open to discussion, and likely include multiple biological actions on cardio and cerebrovascular blood flow, as well as increased levels of Brain Derived Neurotropic Factor.
It is not possible to extrapolate from this study for a protective effect against dementia, but it is certainly a positive step towards multi-domain intervention trials such as the one described by Vellas et al. (ref. 1), that includes physical exercise, cognitive training, nutritional supplements and risk factors management.
A definite proof that such changes in life-style delay cognitive decline and possibly dementia will require a multi-national study over many years, but these low cost changes may be the best intervention from a public health point of view against the expected increased prevalence of cognitive impairment and dementia in our aging populations.
References
1. Vellas B, Gillette-Guyonnet S, Andrieu S. Memory health clinics-a first step to prevention. Alzheimer's & Dementia 2008; 4 (1 Suppl 1); 144-149. [Epub 2007 Dec 21]