Reliable change in neuropsychological test scores is associated with brain atrophy in older adults

The reliable change index (RCI) is a commonly used method for interpreting change in neuropsychological test scores over time. However, the RCI is a psychometric method that, to date, has not been validated against neuroanatomical changes. Longitudinal neuroimaging and neuropsychological data from baseline and one-year follow-up visits were retrieved from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. The RCI was used to identify participants showing reliable decline on memory (ADNI-Mem; N = 450) and executive functioning (ADNI-EF; N = 456) factor scores. For each factor score, two groups (reliable change vs. no reliable change) were matched on potential baseline confounding variables. Longitudinal neuroanatomical data were analysed using tensor-based morphometry. Analysis revealed that reliable change on ADNI-Mem was associated with atrophy in the medial temporal cortex, limbic cortex, temporal lobe and some regions of the parietal lobe. Similar atrophy patterns were found for reliable change on ADNI-EF, except that atrophy extended to the frontal lobe and the atrophy was more extensive and of higher magnitude. The current study not only validates clinical usage of the RCI with neuroanatomical evidence of associated underlying brain change but also suggests patterns of likely brain atrophy when reliable cognitive decline is detected.     

Triangulating causality between childhood obesity and neurobehavior: Behavioral genetic and longitudinal evidence

Childhood obesity is a serious health concern that is not yet fully understood. Previous research has linked obesity with neurobehavioral factors such as behavior, cognition, and brain morphology. The causal directions of these relationships remain mostly untested. We filled this gap by using the Adolescent Brain Cognitive Development study cohort comprising 11,875 children aged 9–10. First, correlations between the age- and sex-specific 95th BMI percentile (%BMIp95) and neurobehavioral measures were cross-sectionally analyzed. Effects were then aggregated by neurobehavioral domain for causal analyses. Behavioral genetic Direction of Causation modeling was used to test the direction of each relationship. Findings were validated by longitudinal cross-lagged panel modeling. %BMIp95 correlated with impulsivity, motivation, psychopathology, eating behavior, and cognitive tests (executive functioning, language, memory, perception, working memory). Greater %BMIp95 was also associated with reduced cortical thickness in frontal and temporal brain areas but with increased thickness in parietal and occipital areas. Similar although weaker patterns emerged for cortical surface area and volume. Behavioral genetic modeling suggested causal effects of %BMIp95 on eating behavior (β = 0.26), cognition (β = 0.05), cortical thickness (β = 0.15), and cortical surface area (β = 0.07). Personality/psychopathology (β = 0.09) and eating behavior (β = 0.16) appeared to influence %BMIp95. Longitudinal evidence broadly supported these findings. Results regarding cortical volume were inconsistent. Results supported causal effects of obesity on brain functioning and morphology. The present study highlights the importance of physical health for brain development and may inform interventions aimed at preventing or reducing pediatric obesity.

Research Highlights

• A continuous measure related to obesity, %BMIp95, has correlations with various measures of brain functioning and structure
• Behavioral genetic and longitudinal modeling suggest causal links from personality, psychopathology, and eating behavior to %BMIp95
• Results also indicate directional links from %BMIp95 to eating behavior, cognition, cortical thickness, and cortical surface area
• Obesity may play a role for healthy brain development during childhood