Table 1.

Summary of underrepresented dimensions (N=60 studies; detailed sample sizes for each included study are available in Multimedia Appendix 3.

Dimension and underrepresented aspect			Supporting studies, n (%)		Interpretive note
DHTa type
	Unidirectional basic media reminders (SMS and telephone)	7 (11.7)		Predominant in several nonsignificant studies; may lack sufficient engagement to sustain adherence
	Context-aware intelligent environments	4 (6.7)		Limited data precludes assessment of potential effectiveness
Population subgroups
	Older adults living alone	1 (1.7)		May require interpersonal support beyond automated reminders
	Low-resource rural settings	2 (3.3)		Infrastructure barriers may limit sustained DHT use
	Frail or cognitively impaired older adults	1 (1.7)		Targeted usability and support needs have not been fully examined
Medication journey					Underrepresented across the entire study base; may represent missed opportunities for adherence support
	Prescription	4 (6.7)
	Refill	3 (5.0)
	Pickup	2 (3.3)
	Storage	1 (1.7)
Adherence measurement
	Unspecified assessment methods	17 (28.3)		Limits comparability of adherence outcomes across studies
Usability evaluation
	No usability assessment reported	49 (81.7)		May impede sustained engagement, particularly among older users with low digital literacy
	Nonstandard usability assessment	10 (16.7)		May limit generalizability
	Formal usability metrics reported	1 (1.7)		—b
Clinical integration
	Bidirectional EHRc interoperability assessed	None		May limit perceived usefulness and integration into care
Follow-up duration
	Long-term outcome assessment (>12 months)	Uncommon		Cannot capture sustained adherence effects

^aDHT: digital health technology.

^bEHR: electronic health record.

^cNot applicable.