Assessment of research waste part 2: wrong study populations- an exemplar of baseline vitamin D status of participants in trials of vitamin D supplementation

• Published in: BMC medical research methodology 2018-10, Vol.18 (1), p.101-14, Article 101
• Main Authors: Bolland, Mark J, Grey, Andrew, Avenell, Alison
• Format: Article
• Language: English
• Subjects: Adult; Deficiency; Diabetes; Dietary Supplements; Fracture; Fractures; Humans; Medical errors; Medical research; Medical Waste - economics; Medical Waste - prevention & control; Medical Waste - statistics & numerical data; Medicine, Experimental; Nutrition research; Osteoporosis; Randomized controlled trials; Randomized Controlled Trials as Topic; Research waste; Sufficiency; Systematic Reviews as Topic; Vitamin D; Vitamin D - administration & dosage; Vitamin D deficiency; Vitamin D Deficiency - drug therapy; Vitamin deficiency; Vitamins - administration & dosage
• ISSN: 1471-2288; 1471-2288
• DOI: 10.1186/s12874-018-0555-1

Research waste can occur when trials are conducted in the wrong populations. Vitamin D deficient populations are most likely to benefit from vitamin D supplementation. We investigated waste attributable to randomised controlled trials (RCTs) of supplementation in populations that were not vitamin D deficient. In December 2015, we searched Pubmed, recent systematic reviews, and three trial registries for RCTs of vitamin D with clinical endpoints in adults, and 25-hydroxvitamin D (25OHD) survey data relevant to large (N ≥ 1000) RCTs. We investigated the proportion of RCTs that studied vitamin D deficient populations, temporal trends in baseline 25OHD, and whether investigators in large RCTs considered relevant 25OHD survey data or systematic reviews in their trial justifications. Of 137 RCTs of vitamin D with clinical endpoints, 118 (86%) reported baseline mean/median 25OHD, which was  40 nmol/L. Baseline 25OHD increased over time. Before 2006, 38%, 62%, 0% and 0% of RCTs had baseline 25OHD