RT Journal
A1 Middleton LE
T1 PHysical activity, vascular health, and cognitive impairment—reply
JF Archives of Internal Medicine
JO Archives of Internal Medicine
YR 2012
FD January 9
VO 172
IS 1
SP 83
OP 84
DO 10.1001/archinternmed.2011.616
UL http://dx.doi.org/10.1001/archinternmed.2011.616
AB 
My colleagues and I thank Dr Smith for his interest in our article.1 Dr Smith raises the possibility that cardiorespiratory fitness may mediate the relationship between activity energy expenditure (AEE) and cognitive impairment. Though physical activity is 1 predictor, AEE itself is only weekly associated with cardiorespiratory fitness.2 As a result, other mechanisms such as alteration in brain-derived neurotrophic factor levels and improvement of vascular function are likely to contribute to the relationship.3