Digital N-of-1 Trials and their Application in Experimental Physiology

Traditionally, studies in experimental physiology have been conducted in small groups of human participants, animal models or cell lines. Important challenges include achieving sufficient statistical power in statistical hypothesis tests of small sample sizes and identifying optimal study designs. Here, we introduce N-of-1 trials as an innovative study design which can have high relevance to innovate and improve studies in experimental physiology. N-of-1 trials are multi-crossover trials in single participants that allow valid statistical inference on the individual level. Also, series of N-of-1 trials conducted on multiple study participants can be aggregated for population-level inference and provide a more efficient study design compared to standard randomized controlled trials. In this manuscript, we first introduce key components and design features of N-of-1 trials. Then we lay out how N-of-1 trials can be analyzed statistically and give different examples of their applicability in experimental physiological studies. In summary, we provide here an overview of all main components for designing N-of-1 trials, give direct examples in experimental physiology and practical recommendations on their proper use.