Table 1.

Conceptual framework underlying user engagement metrics based on the study by O’Brien and Toms, 2013.

Conceptual framework and metric names		Definition
Point of engagement
	Activity delay		Days from consent date to first active day
Period of engagement
	User activity ratio		Number of active days divided by number of potentially active days (here 180)
	Longevity		Days from first until last active day (maximum=180)
	Recency		Average number of days between entries
	Regularity		Coefficient of variation of number of days between entries
Discontinuation
	Persistence		Days until 28 days discontinuation
	Dropouts		Illustrated in Figure 1
Reengagement
	Engagement pattern		Illustrated in Figure 2