Regression-based formulas for predicting change in memory test scores in healthy older adults: Comparing use of raw versus standardized scores

Brain volume loss after cranial irradiation: a controlled comparison study between photon vs proton radiotherapy for WHO grade 2-3 gliomas

PURPOSE

Radiation therapy (RT) is an integral treatment component in patients with glioma but associated with neurotoxicity. Proton RT (PRT), as compared with photon RT (XRT), reduces excess radiation to nontarget tissue. We used a retrospective method to evaluate brain imaging metrics of neurotoxicity after treatment with PRT and XRT for glioma.

METHODS

We analyzed brain volume change in thirty-four patients with WHO grade 2-3 gliomas treated with either PRT (n = 17) or XRT (n = 17). Both groups were carefully matched by demographic/clinical criteria and assessed longitudinally for two years post-radiotherapy. Brain volume change was measured as ventricular volume expansion in the tumor free hemisphere (contralateral to RT target) as a proxy indicator of brain volume loss. We further assessed the impact of volumetric changes on cognition in PRT patients, who completed neuropsychological testing as part of an outcome study.

RESULTS

We found significant ventricular volume increases in the contralesional hemisphere in both groups at two years post-RT (F(1, 31) = 18.45, p < 0.000, partial η2 = 0.373), with greater volume change observed in XRT (26.55%) vs. PRT (12.03%) (M = 12.03%, SD = 16.26; F(1,31) = 4.26, p = 0.048, partial η2 = 0.121). Although, there was no group-level change on any cognitive test in PRT treated patients, individual changes on cognitive screening, working memory, processing speed and visual memory tasks correlated with contralesional brain volume loss.

CONCLUSION

This study suggests progressive brain volume loss following cranial irradiation, with greater severity after XRT vs. PRT. Radiation-induced brain volume loss appears to be associated with measurable cognitive changes on an individual level. Prospective studies are warranted to validate these findings and their impacts on long-term cognitive function and quality of life. An improved understanding of the structural and functional consequences of cranial radiation is essential to develop neuroprotective strategies.

Derivation of Indices of Cognitive Change Among Hispanic Adults and Elders

Importance

Determining the influence of race and ethnicity on change in cognitive test performance has significant implications for clinical practice and research in populations at risk for Alzheimer disease.

Objective

To evaluate the significance of race and ethnicity in predicting longitudinal cognitive test performance and to develop models to support evidence-based practice.

Design, Setting, and Participants

This prognostic study included baseline and 24-month follow-up data that were obtained from the Health and Aging Brain Study-Health Disparities (HABS-HD) study, an ongoing longitudinal observational study of aging and dementia in a multiracial, multiethnic cohort. Participants included community-dwelling adults and elders living in the Dallas and Fort Worth metropolitan area who were Hispanic and non-Hispanic adults older than the age of 50 years and were cognitively unimpaired.

Exposure

The primary exposure of interest was time, measured in months.

Main Outcomes and Measures

Demographic variables included age, sex, education, and race and ethnicity. Cognitive domains included attention and working memory, processing speed, language, memory, and executive functioning. Linear regression models predicted follow-up performance from baseline performance and demographic variables for 13 commonly used neuropsychological tests. Follow-up testing was the primary outcome for all domains. Raw scores from 13 standardized tests were used for analyses.

Results

This study included 799 adults who were cognitively unimpaired (352 Hispanic individuals [44.1%]; 447 non-Hispanic individuals [55.9%]; 524 female [65.6%]; mean [SD] age, 65.4 [8.1] years). In the regression models, all 13 follow-up scores were significantly predicted from their respective baseline scores and demographic variables. Baseline performance and education were the most consistent predictors of follow-up scores, contributing to all 13 models. Age was significantly associated with follow-up in 11 models, and sex was significant in 5 models. Race and ethnicity contributed to 10 of 13 models, with Hispanic participants predicted to have poorer follow-up scores than their non-Hispanic White counterparts on each test.

Conclusions and Relevance

In this longitudinal study of cognitive change in Hispanic and non-Hispanic older adults who were cognitively unimpaired, standardized regression-based models were influenced by multiple demographic variables, including race and ethnicity. These findings highlight the importance of including race and ethnicity in such cognitive change models. This ability to accurately predict cognitive change is expected to become increasingly important as clinical practice and clinical trials need to become more diverse and culturally appropriate in this burgeoning global medical and societal crisis.

Assessing and validating reliable change across ADNI protocols

OBJECTIVE

Reliable change methods can aid in determining whether changes in cognitive performance over time are meaningful. The current study sought to develop and cross-validate 12-month standardized regression-based (SRB) equations for the neuropsychological measures commonly administered in the Alzheimer's Disease Neuroimaging Initiative (ADNI) longitudinal study.

METHOD

Prediction algorithms were developed using baseline score, retest interval, the presence/absence of a 6-month evaluation, age, education, sex, and ethnicity in two different samples (n = 192 each) of robustly cognitively intact community-dwelling older adults from ADNI - matched for demographic and testing factors. The developed formulae for each sample were then applied to one of the samples to determine goodness-of-fit and appropriateness of combining samples for a single set of SRB equations.

RESULTS

Minimal differences were seen between Observed 12-month and Predicted 12-month scores on most neuropsychological tests from ADNI, and when compared across samples the resultant Predicted 12-month scores were highly correlated. As a result, samples were combined and SRB prediction equations were successfully developed for each of the measures.

CONCLUSIONS

Establishing cross-validation for these SRB prediction equations provides initial support of their use to detect meaningful change in the ADNI sample, and provides the basis for future research with clinical samples to evaluate potential clinical utility. While some caution should be considered for measuring true cognitive change over time - particularly in clinical samples - when using these prediction equations given the relatively lower coefficients of stability observed, use of these SRBs reflects an improvement over current practice in ADNI.

Application of Different Standard Error Estimates in Reliable Change Methods

OBJECTIVE

This study attempted to clarify the applicability of standard error (SE) terms in clinical research when examining the impact of short-term practice effects on cognitive performance via reliable change methodology.

METHOD

This study compared McSweeney's SE of the estimate (SEest) to Crawford and Howell's SE for prediction of the regression (SEpred) using a developmental sample of 167 participants with either normal cognition or mild cognitive impairment (MCI) assessed twice over 1 week. One-week practice effects in older adults: Tools for assessing cognitive change. Using these SEs, previously published standardized regression-based (SRB) reliable change prediction equations were then applied to an independent sample of 143 participants with MCI.

RESULTS

This clinical developmental sample yielded nearly identical SE values (e.g., 3.697 vs. 3.719 for HVLT-R Total Recall SEest and SEpred, respectively), and the resultant SRB-based discrepancy z scores were comparable and strongly correlated (r = 1.0, p < .001). Consequently, observed follow-up scores for our sample with MCI were consistently below expectation compared to predictions based on Duff's SRB algorithms.

CONCLUSIONS

These results appear to replicate and extend previous work showing that the calculation of the SEest and SEpred from a clinical sample of cognitively intact and MCI participants yields similar values and can be incorporated into SRB reliable change statistics with comparable results. As a result, neuropsychologists utilizing reliable change methods in research investigation (or clinical practice) should carefully balance mathematical accuracy and ease of use, among other factors, when determining which SE metric to use.

Development and Preliminary Validation of Standardized Regression-Based Change Scores as Measures of Transitional Cognitive Decline

OBJECTIVE

An increasing focus in Alzheimer's disease and aging research is to identify transitional cognitive decline. One means of indexing change over time in serial cognitive evaluations is to calculate standardized regression-based (SRB) change indices. This paper includes the development and preliminary validation of SRB indices for the Uniform Data Set 3.0 Neuropsychological Battery, as well as base rate data to aid in their interpretation.

METHOD

The sample included 1,341 cognitively intact older adults with serial assessments over 0.5-2 years in the National Alzheimer's Coordinating Center Database. SRB change scores were calculated in half of the sample and then validated in the other half of the sample. Base rates of SRB decline were evaluated at z-score cut-points, corresponding to two-tailed p-values of .20 (z = -1.282), .10 (z = -1.645), and .05 (z = -1.96). We examined convergent associations of SRB indices for each cognitive measure with each other as well as concurrent associations of SRB indices with clinical dementia rating sum of box scores (CDR-SB).

RESULTS

SRB equations were able to significantly predict the selected cognitive variables. The base rate of at least one significant SRB decline across the entire battery ranged from 26.70% to 58.10%. SRB indices for cognitive measures demonstrated theoretically expected significant positive associations with each other. Additionally, CDR-SB impairment was associated with an increasing number of significantly declined test scores.

CONCLUSIONS

This paper provides preliminary validation of SRB indices in a large sample, and we present a user-friendly tool for calculating SRB values.

Individual changes in visual performance in non-demented Parkinson's disease patients: a 1-year follow-up study

Cognitive deficits in Parkinson's disease (PD) are heterogeneous entities, and the cognitive status fluctuates over time. However, individual changes in longitudinal cognitive performance in PD are not fully understood. We evaluated three visual indices (visuoperception, visuoconstruction, and visuospatial ability) and four cognitive domains (attention/working memory, executive function, memory, and language) at baseline (Time1) and at 1-year follow-up (Time2) in 36 patients with PD and 32 healthy controls (HCs). To explore the magnitude and frequency of cognitive changes, we analyzed data using the simple difference method and the standardized regression-based method. We also explored the correlations between changes in test scores and several clinical predictors, using logistic regression analysis. At 1 year, patients with PD showed higher rates of change in scores on several cognitive tests, especially the Incomplete Letters test of visuoperception, compared to HCs. After adjusting for demographic variables, the visuoperceptual change was 61.1% overall, with the largest effect size. The changes in scores of visuoperception correlated with those of memory (r = 0.672, p < 0.001), language (r = 0.389, p < 0.05), and visuospatial ability (r = 0.379, p < 0.05). The severity of olfactory disturbance, the MDS-UPDRS Part I score, and younger PD onset predicted the significant changes observed in the Incomplete Letters test scores. Visuoperception changed more in non-demented PD patients than in HCs at 1-year follow-up. The changes in visuoperception could relate to involvement of the ventral occipitotemporal pathway, the more widespread temporal lobe, and brain reserve in PD.