Skin carotenoid content is associated with speed of processing in cognitively normal older adults

Background Brain and retinal carotenoid content have been linked to cognitive function in older adults. Although skin carotenoid is correlated with retinal content, the relationship of skin carotenoid and cognition in older adults is unknown. Measurement of skin carotenoid is non‐invasive, quick, and easy to obtain. The purpose of this study was to evaluate the relationship between skin carotenoid concentration and cognitive performance in a population of cognitively normal, older adults. Method Baseline data from 101 cognitively normal older adults participating in a nutrition intervention study (Nutrition Interventions for Cognitive Enhancement study; NICE study) were analyzed. Skin carotenoid content was measured using pressure‐mediated reflection spectroscopy by the Veggie Meter® (Longevity Link Corporation). A comprehensive cognitive battery was conducted by a trained psychometrician. The NICE cognitive battery includes three age and education corrected cognition tests from the NIH‐Toolbox Cognition Battery – the Pattern Comparison Processing Speed, Flanker Inhibitory Control and Attention, and Dimensional Change Card Sort Tests. We tested the relationship between skin carotenoid content and corrected NIH‐Toolbox test T‐scores using ordinary least squares regression adjusted for sex and BMI. Statistical model assumptions were evaluated through residual analyses. Statistical analyses were performed using R (v. 3.6.2; R Foundation, Vienna, Austria) and statistical significance was set at p < 0.05. Result Most participants were female (80.2%) and overweight (BMI of 28.3 ± 4.5 kg/m 2 ) with a mean age of 71.8 ± 4.9 years. Mean skin carotenoid content was 275.1 ± 81.8. Higher skin carotenoid content was correlated with faster speed of processing (Pattern Comparison Processing Speed Test: b = ‐0.21, p = 0.03), but skin carotenoids were not related to tests of attention or executive function (Flanker Inhibitory Control and Attention Test: b = 0.12, p = 0.26 and Dimensional Change Card Sort Test: b = 0.07, p = 0.47). Conclusion The measurement of skin carotenoids may be a useful tool to identify a modifiable risk factor for Alzheimer’s Disease. These findings will be further investigated utilizing the final sample size of the NICE Study (n=200).