Does cerebral blood flow decline in healthy aging? A PET study with partial-volume correction

It remains a matter of controversy as to whether cerebral perfusion decline s with healthy aging. In vivo imaging with PET permits quantitative evaluat ion of brain physiology; however, previous PET studies have inconsistently reported aging reductions in cerebral blood flow (CBF), oxygen metabolism, and glucose metabolism. In part, this may be because of a lack of correctio n for the dilution effect of age-related cerebral volume loss on PET measur ements, Methods: CBF PET scans were obtained using [O-15]H2O in 27 healthy individuals (age range, 19-76 y) and corrected for partial-volume effects f rom cerebral atrophy using an MR-based algorithm. Results: There was a sign ificant difference (P = 0.01) in mean cortical CBF between young/midlife (a ge range, 19-46 y; mean +/- SD, 56 +/- 10 mL/100 mL/min) and elderly (age r ange, 60-76 y; mean +/- SD, 49 +/-. 2.6 mL/100 mL/min) subgroups before cor recting for partial-volume effects. However, this group difference resolved after partial-volume correction (young/midlife: mean +/- SD, 62 +/- 10 mL/ 100 mL/min; elderly: mean +/- SD, 61 +/- 4.8 mL/100 mL/min; P = 0.66). When all subjects were considered, a mild but significant inverse correlation b etween age and cortical CBF measurements was present in the uncorrected but not the corrected data. Conclusion: This study suggests that CBF may not d ecline with age in healthy individuals and that failure to correct for the dilution effect of age-related cerebral atrophy may confound interpretation of previous PET studies that have shown aging reductions in physiologic me asurements.