Table 2.

Messages per unique patient by year.

Message type	Mean messages per unique patient by year (SD, 95% CI)						P valuea
	2013	2014	2015	2016	2017
Provider message responses from all specialty and primary care	3.6 (5.3, 3.5-3.6)	4.2 (6.6, 4.1-4.2)	4.3 (6.3, 4.3-4.3)	4.7 (6.7, 4.6-4.7)	4.9 (6.9, 4.9-4.9)	<.001
Provider-initiated messages from all specialty and primary care	2.1 (2.0, 2.1-2.1)	2.5 (2.7, 2.5-2.5)	2.8 (3.1, 2.8-2.8)	3.2 (3.6, 3.2-3.3)	3.7 (4.1, 3.7-3.7)	<.001

^aH0: mean messages are equal across years.