Sex-specific 25-hydroxyvitamin D threshold concentrations for functional outcomes in older adults: PRoject on Optimal VItamin D in Older adults (PROVIDO)

• Published in: The American Journal of Clinical Nutrition
• Main Authors: Shardell, Michelle, Cappola, Anne R, Guralnik, Jack M, Hicks, Gregory E, Kritchevsky, Stephen B, Simonsick, Eleanor M, Ferrucci, Luigi, Semba, Richard D, Shaffer, Nancy Chiles, Harris, Tamara, Eiriksdottir, Gudny, Gudnason, Vilmundur, Cotch, Mary Frances, Orwoll, Eric, Ensrud, Kristine E, Cawthon, Peggy M
• Other Authors: The Age, Gene/Environment Susceptibility-Reykjavik, Icelandic Heart Association, National Eye Institute Intramural Research Program, Health, Aging, and Body Composition, NIA Intramural Research Program, NIA, The Invecchiare in Chianti, Ministry of Health, Italy, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Center for Research Resources, NIH Roadmap for Medical Research, SOF
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2021
• Subjects: Nutrition and Dietetics; Medicine (miscellaneous); Iceland
• Online Access: http://dx.doi.org/10.1093/ajcn/nqab025; http://academic.oup.com/ajcn/article-pdf/114/1/16/38874130/nqab025.pdf

ABSTRACT Background Threshold serum 25-hydroxyvitamin D [25(OH)D] concentrations for extraskeletal outcomes are uncertain and could differ from recommendations (20–30 ng/mL) for skeletal health. Objectives We aimed to identify and validate sex-specific threshold 25(OH)D concentrations for older adults’ physical function. Methods Using 5 large prospective, population-based studies—Age, Gene/Environment Susceptibility-Reykjavik (n = 4858, Iceland); Health, Aging, and Body Composition (n = 2494, United States); Invecchiare in Chianti (n = 873, Italy); Osteoporotic Fractures in Men (n = 2301, United States); and Study of Osteoporotic Fractures (n = 5862, United States)—we assessed 16,388 community-dwelling adults (10,376 women, 6012 men) aged ≥65 y. We analyzed 25(OH)D concentrations with the primary outcome (incident slow gait: women <0.8 m/s; men <0.825 m/s) and secondary outcomes (gait speed, incident self-reported mobility, and stair climb impairment) at median 3.0-y follow-up. We identified sex-specific 25(OH)D thresholds that best discriminated incident slow gait using machine learning in training data (2/3 cohort-stratified random sample) and validated using the remaining (validation) data and secondary outcomes. Results Mean age in the cohorts ranged from 74.4 to 76.5 y in women and from 73.3 to 76.6 y in men. Overall, 1112/6123 women (18.2%) and 494/3937 men (12.5%) experienced incident slow gait, 1098/7011 women (15.7%) and 474/3962 men (12.0%) experienced incident mobility impairment, and 1044/6941 women (15.0%) and 432/3993 men (10.8%) experienced incident stair climb impairment. Slow gait was best discriminated by 25(OH)D <24.0 ng/mL compared with 25(OH)D ≥24.0 ng/mL in women (RR: 1.29; 95% CI: 1.10, 1.50) and 25(OH)D <21.0 ng/mL compared with 25(OH)D ≥21.0 ng/mL in men (RR: 1.43; 95% CI: 1.01, 2.02). Most associations between 25(OH)D and secondary outcomes were modest; estimates were similar between validation and training datasets. Conclusions Empirically identified and ...