Price JC, Weissfeld LA, Bi W, Cohen AD, Saxton JA, Snitz BE, Berginc M, DeKosky ST, Mathis CA, Klunk WE.
Evaluation of longitudinal PiB data using linear mixed models.
Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;
Objectives: This work applies linear mixed modeling (LMM) to analyze longitudinal amyloid (As) imaging data
acquired at baseline (BL) and annual follow-up over 2 years. LMM accounts for correlation among repeated
measures, includes all data and subject groups and assesses effects of time and group.
Methods: [C-11]PiB PET imaging was performed (i.e., SUVR40-60 outcome, cerebellum reference). Manual
region delineation and CSF correction was based on each subjectfs MRI. Thirteen regions were examined that
included primary cortical areas, as well as anterior ventral striatum and pons. Data were acquired in normal control
[NC, 72}9 yrs at BL N = 81 (23 PiB+); Yr1 N = 23 (11 PiB+); Yr2 N = 44 (14 PiB+)], mild cognitive impairment [MCI,
69}9 yrs at BL N = 48 (30 PiB+); Yr1 N = 25 (16 PiB+); Yr2 N = 10 (6 PiB+)] and Alzheimer's disease [AD, all PiB+,
71}11 yrs at BL N = 41; Yr1 N = 15; Yr2 N = 5] subjects. Statistical analyses were performed (SAS software) for each
ROI with 5 subject groups: PiB- NC, PiB+ NC, PiB- MCI, PiB+ MCI, AD (PiB+).
Results: All PiB+ groups (NC, MCI or AD) showed evidence of PiB retention increases in cortical areas within the
2-year follow-up that was most notable for PiB+ MCI subjects. The PiB+ MCI annual increases, for several regions,
were greater than those for PiB+ NC and AD (albeit small Yr2 sample). SUVR interval differences as large as
0.29-0.30 SUVR units were observed in precuneus and anterior cingulate for PiB+ MCI subjects.
Conclusions: The LMM analysis provides further evidence of detectable in vivo As plaque accumulation in NC,
MCI and AD, within a 2-year follow-up period. This work demonstrates the power of LMM to enable further
understanding of early and sustained amyloid deposition in human brain through utilization of all data, i.e., very
PiB+ and PiB-, to assess time and group effects.