Harrison, Theresa M.

Importance Amyloid positron emission tomography (PET) is increasingly used in research and clinical settings to determine the etiology of cognitive decline and eligibility for amyloid-targeting therapies. To assist with amyloid PET evaluation and to guide clinical decision-making, images can be quantified in a standardized unit called Centiloid, the interpretation of which can vary according to the method and threshold used. Objective To collect Centiloid values from available studies and determine robust positivity cutoffs using data-driven methods and correspondence with visual reads. Data Sources PubMed search (October 2024) identified studies with Centiloid values. Corresponding authors were invited to share individual participant data. Additional data were obtained through access-controlled repositories and conference outreach (July 2024-July 2025). Study Selection Studies were included if they provided Centiloids, radiotracer, age, and sex. Data Extraction and Synthesis Each study was analyzed using a unified statistical pipeline; study estimates were pooled using random-effects meta-analysis. Main Outcomes and Measures Gaussian mixture models (GMMs) were fitted to Centiloid values for each study. In studies with a bimodal distribution (per integrated completed likelihood), single cutoffs for positivity were set as mean plus 2 SDs of the lower gaussian component. Using GMMs, a double-cutoff approach defined a lower certainty range using a 90% posterior probability cutoff for assignment to the low (amyloid-negative) vs high (amyloid-positive) component. An alternative Centiloid cutoff was derived from maximizing the correspondence (Cohen κ) with the binary visual reads when available. Results This meta-analysis included cross-sectional amyloid PET scans acquired with 5 radiotracers from 49 227 participants across 53 studies from 15 countries (mean age, 71 years; 54% female, 62% cognitively impaired). The data-driven GMM approach identified a bimodal distribution in 51 studies (n = 48 786), resulting in a single cutoff for positivity of 18 Centiloids (95% CI,16-19; I 2 = 97%). The double-cutoff approach revealed high confidence for interpreting scans as negative when Centiloid values were lower than 11 (95% CI, 9-13; I 2 = 95%) and interpreting scans as positive if Centiloid values were higher than 26 (95% CI, 24-28; I 2 = 95%). In analyses of correspondence with binary (positive or negative) visual reads of amyloid PET scans (n = 35 045; 36 studies), Centiloids were highly predictive of visual positivity (Cohen κ, 0.86; 95% CI, 0.83-0.89; I 2 = 96%) with a cutoff of 27 Centiloids (95% CI, 24-30; I 2 = 80%). Conclusions and Relevance In this individual participant data meta-analysis, positivity cutoffs converged around 18 Centiloids (data-driven) and 27 Centiloids (visual reads). Findings from a double-cutoff analysis suggest that scans in the 11 to 26 Centiloid range should be interpreted with caution depending on the context of use.

Importance Multidomain lifestyle interventions slow cognitive decline in at-risk older adults, but effects on cerebrovascular injury and whether any effect differs by age or across magnetic resonance imaging (MRI) markers remain unclear. Objectives To test whether a structured multidomain lifestyle intervention, vs a self-guided program, alters trajectories of cerebrovascular MRI markers and whether baseline diffusion MRI estimates subsequent vascular injury. Design, Setting, and Participants POINTER Imaging was a prespecified secondary imaging analysis of the US POINTER (US Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk) randomized clinical trial conducted at multiple US sites. Starting August 1, 2020, and continuing until March 1, 2023, all newly enrolled US POINTER trial participants who met criteria, including being 60 to 79 years of age and at increased risk for cognitive decline, were given the opportunity to enroll in POINTER Imaging. Annual MRIs were performed at baseline and up to 2 follow-up visits at 12 and 24 months. The imaging study ended May 14, 2025. Interventions Structured multidomain lifestyle arm (supervised exercise, dietary counseling, cognitive and social engagement, and health coaching) vs self-guided educational arm. Main Outcomes and Measures Primary outcomes were cerebrovascular MRI markers of global white matter free water (FW), fractional anisotropy (FA), peak width of skeletonized mean diffusivity (PSMD), analysis along the perivascular space (ALPS) index, white matter hyperintensity (WMH) volume, and incident cerebral microbleeds (CMBs). Age-group analyses (<70 vs ≥70 years) were prespecified. Linear mixed-effects models tested time, intervention arm, age group, and interactions for continuous outcomes; logistic regression evaluated incident CMBs. All analyses were adjusted for sex, hypertension, diabetes, and smoking and were conducted for the evaluable population. Data were analyzed September 5 to December 11, 2025. Results For 959 participants included in the analysis, the mean (SD) age was 68 (5) years, and 594 (61.9%) were female. A significant time × arm × age group interaction was observed for FW (β = 0.050; SE = 0.018; P = .006). In participants younger than 70 years, the structured intervention, compared with the self-guided intervention, attenuated the FW increase over time (β = −0.031; SE = 0.012; P = .009); no intervention arm difference was observed in participants aged 70 years or older (β = 0.019; SE = 0.014; P = .18). No intervention-related interactions were detected (eg, time × intervention arm interaction) for WMH (β = 0.002; SE = 0.016; P = .90), FA (β = 0.016; SE = 0.016; P = .30), PSMD (β = −0.011; SE = 0.021; P = .60), or ALPS (β = 0.006; SE = 0.021; P = .79). Overall, greater odds of incident CMBs were associated with higher baseline FW (odds ratio, 1.63 [95% CI, 1.24-2.14]; P < .001) and PSMD (odds ratio, 1.40 [95% CI, 1.08-1.81]; P < .001). Greater WMH progression was associated with higher baseline FW (β = 0.014; SE = 0.006; P = .02) and lower baseline FA (β = −0.018; SE = 0.006; P = .004). Conclusions and Relevance In this secondary imaging analysis of a randomized clinical trial, FW was the cerebrovascular MRI marker most responsive to lifestyle intervention in adults 60 to 70 years of age, showing attenuated small-vessel disease–related injury. Findings suggested greater microvascular benefit when intensive lifestyle intervention is implemented earlier in late life. Trial Registration ClinicalTrials.gov Identifier: NCT03688126