Exploration of smart adherence-monitoring methods in vitamin D-deficient patients: A pilot feasibility clinical study.

Treatment adherence is an underestimated determinant of treatment success. Poor treatment adherence can also affect the efficacy of clinical trials. A combination of multiple adherence-monitoring methods is required to ensure robustness. We investigated whether multiple adherence-monitoring methods, including a novel smartwatch-based monitoring method, would yield reliable and concordant results. In this open, randomized, decentralized clinical trial, vitamin D-deficient individuals were randomized to an App - only group (an electronic medication diary) or an App + Watch group (i.e., App and smartwatch-based monitoring) groups after a week run-in period. The participants received vitamin D supplements (1000 IU) for 12 weeks (two consecutive periods of 6 weeks) with two pill counts (at the sixth week) and biweekly blood samplings for serum 25(OH) vitamin D concentration. Adherence was assessed and compared between the methods. Sixteen participants were enrolled, of which 13 completed the study. Serum 25(OH) vitamin D levels comparably increased in both groups until the first 7 weeks but trended higher in the App + Watch group in the second period. The number of doses recorded by the pill count and App did not differ significantly between the run-in and Period 1 (p = 0.5534) but became significantly discrepant in Period 2 (p = 0.0225). In contrast, the concordance for smartwatch-based monitoring was consistent in either period (p = 0.5898 and p = 0.5839, respectively). We explored multiple adherence-monitoring methods in this pilot feasibility clinical study. Smartwatch-based adherence monitoring may be an objective and sensitive method for measuring treatment adherence.