Comparison of skin carotenoid content scores and dietary intake between cognitively normal older adults and older adults with Alzheimer’s Disease: A matched‐pair analysis

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AbstractBackgroundAlzheimer’s Disease (AD) is a systemic metabolic disease with a variable number and type of clinical symptoms mostly impacting the brain. Skin carotenoid content (SCC) is an objective measure of carotenoid‐containing fruit and vegetable intake that has been validated in diverse populations. Our previous findings suggest SCC scores are impacted by various metabolic disease states. Therefore, our objective was to analyze SCC scores and dietary intake across matched pairs including unimpaired adults and those with AD.MethodBaseline data from two dietary interventions (NCT03860792, NCT03841539) were analyzed. Pairs are exact matches for sex, race/ethnicity, and education and are matched within two years of age and 4 kg/m2 body mass index. Each pair (n = 12 pairs) includes one cognitively normal (MMSE > 25), community dwelling older adult (‘CN’) and one community dwelling older adult with AD (‘AD’). Baseline self‐reported dietary intake data (3‐day food records) were collected, reviewed, and entered into the Nutrition Data System for Research (NDSR 2019) database by a Registered Dietitian. SCC scores were collected through pressure‐mediated reflection spectroscopy via VeggieMeter® (Longevity Link Corporation, Holladay, UT). Two‐sample independent t‐tests assuming unequal variances were used to compare differences in SCC scores and dietary intake. Significance was set at p = 0.05.ResultThere was a significant difference in SCC scores between matched pairs (SCC scores: CN 284.25, AD 207.67, p = 0.008). There was no difference between pairs for total daily energy (kcal/day; p = 0.60), fat (g/day; p = 0.91), carbohydrate (g/day; p = 0.85), or protein (g/day; p = 0.26) intake. Both groups had similar food group intake (p‐value range 0.09‐0.79), including all fruit and vegetable groups except CN had higher intake of non‐citrus fruit (p = 0.046). Total fruit (p = 0.09) and fruit plus vegetable (p = 0.24) were not different between pairs. Dietary intake by individual carotenoid was not significantly different (total vitamin A, p = 0.48; beta‐carotene, p = 0.49; alpha‐carotene, p = 0.57; beta‐cryptoxanthin, p = 0.60; lutein plus zeaxanthin, p = 0.07; lycopene, p = 0.37).ConclusionIndividuals with AD have lower carotenoid skin content compared to matched cognitively unimpaired individuals. These differences are not explained by differences in diet suggesting that AD may be associated with disease‐associated biochemical features that are metabolism‐related and not limited to the brain.