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Beckman Institute & Department of Psychology University of Illinois
Effects of Exercise & Physical Activity on Brain & Cognitive Function: A Brief Review of the Literature!
Art Kramer & colleagues
We may have a problem encouraging increases in physical activity & exercise for Americans …..!
Roadmap for Today …..! • In epidemiological studies has physical activity been shown to be associated with reducing the risk of developing Alzheimer’s disease or age-related cognitive decline ?!
• On the basis of observational studies is it clear what kinds of physical activities are most effective ?!
• What do we know from randomized controlled interventions with regard to exercise effects on brain & cognition ?!
• Is it known what kinds of physical activity & what durations & frequencies of such activities produce the greatest changes in brain & cognition ?!
• Is there a point of no-return with regard to exercise benefits on cognition and brain?!
• What do we know about the cellular & molecular mechanisms that underlie exercise effects on cognition?!
• What studies need to be done to further advance our understanding of the link between exercise & cognition ?!
I. In epidemiological studies has physical activity been shown to be associated with reducing the risk of developing Alzheimer’s disease or age-related cognitive decline?!
ANSWER: Yes (most of the time)!
Weuve et al (2004)!
Yaffe at al (2001)!
Karp et al (2006)!
• a study of 776 > 75 year olds over the course of 6 years - activities at time 1, dementia at time 2.!
Qualification: Not all epidemiological studies find a significant relationship between physical activity/exercise & cognition/dementia!
Why not ?!
• Assessment of activity/exercise – mostly self report!• Frequency, duration, intensity, variety not always assessed!
• Assessment of cognition – mostly general (e.g. MMSE)!
• Potential interaction of social, cognitive, diet and other factors!
• Age, health, gender, socioeconomic factors!
• Genetic factors (status of apoe occasionally assessed)!
II. From these observational studies is it clear which kinds of physical activities are most effective?!
Answer: Different activities are rarely compared …!
• An exception – walking!• Has often shown dose responses effects!
• Activities which result in substantial exertion have been found to sometimes lead to greater cognitive benefits!
• But most studies examine “physical activities” rather than fitness (with objective measures)!
• Speculation – physical activities which are also social & intellectually challenging might be worth examining (e.g. dance, etc)!
III. In clinical studies or trials with an exercise intervention, what are the effects of physical activity on brain & cognitive measures?!
Effect Size Estimates as a Function of Task Type and Group
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Executive Controlled Spatial Speed
Task Type
Eff
ec
t S
ize
(g
)
Control
Exercise
• Across studies that find positive effects of fitness training on cognition the cognitive benefits are quite broad – with larger benefits for some cognitive processes …!
Colcombe & Kramer (2003)!
Although much is known about fitness training effects on brain function with non-human animals there is a dearth of knowledge of fitness training effects with humans …….!
Colcombe et al, 2006!
Pereira et al, 2007!
Effects of fitness training on performance & brain function:!
Percent Decrease in Interference Effect
0
2
4
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Toners Walkers
Training Group
Per
cent
Dec
reas
e in
Inte
rfer
ence
((T1
-T2
)/T1)
*100
)
Flanker / Selective Attention Task Sternberg Memory Search Task!
Slop
e ch
ange
(pe
rcen
t)!
Colcombe et al., 2004!
IV. Is it known what kinds of physical activity & what durations & frequencies of such activities produce the greatest changes in brain & cognition?!
• Aerobic activities have been main focus of fitness training research (given link to animal research) but … (resistance training)!
Cassilhas et al, 2007!
Liu-Ambrose et al, 2008!
Some moderators of:!
Fitness Training Cognition!
• Cognitive task improvement was larger when aerobic training was coupled with resistance training!
• Cognitive improvement was larger when session > 30 minutes!
• Cognitive improvement was larger when subjects > 65 years of age!
• Cognitive improvement was larger for women than men!
but lots of qualifications …..!
Colcombe & Kramer, 2003!
V. Is there a point of no-return with regard to exercise benefits on cognition and brain?!
Heyn et al (2004)!Early Alzheimer’s Patients!
Multiple Sclerosis Patients!
Prakash et al (2009)!
Parkinson’s Patients! Uc et al, (2008)!
• Differences in gray matter volume & white matter integrity (via DTI) as a function of fitness are correlated with processing speed!
• Fitness related differences in fMRI activation pattern are correlated with measures of attentional control and inhibition!
VI. What about exercise effects on brain & cognitive function of children?!
Chaddock et al (submitted)!
VII. What do we know about the cellular & molecular mechanisms that underlie exercise effects on cognition?!
Brown et al, 2003!ALSO ……!
• increases in neurotrophins (e.g. BDNF, IGF1, etc)!• enhanced synaptogenesis!• enhanced angiogenesis!• increased production of various neurotransmitters!• reduced beta amyloid protein in mouse knock out models!• enhanced learning & memory !
VIII. What studies need to be done to further advance our understanding of the link between exercise & cognition ?!
• Studies that systematically examine type of exercise, duration, & intensity,!
• Studies that include a theoretically-based & comprehensive assessment of cognition (including outside the lab …. ),!
• Studies that include state-of-the-art & multimodal measures of brain function & structure,!
• Studies that include biomarkers of inflammation, neurotrophic proteins, & potentially relevant genes,!
• Studies that examine potentially important demographic & lifestyle factors – e.g. education, SES, social support, diet, intellectual challenge, life stresses, physical activity/exercise history, etc. !
