Smartphone barrier: uncovering the digital divide in mHealth prevention among disadvantaged middle-aged and older-aged UK communities.

Objectives: To investigate the response to an invitation to participate in a blended mobile Health intervention among adults living in deprived areas. Design: Secondary analysis of recruitment data from a randomised controlled trial. Setting: A primary care population from disadvantaged geographies in the UK. Participants: Individuals in mid-to-late life at increased risk of developing dementia based on their risk profile. Interventions: Invitation by letter from GP, followed by a text reminder by phone. Main outcome measures: (1) Response rate to the invitation. (2) Association of response with GP practice size, area-level deprivation and COVID-19 restrictions. (3) Reasons for non-participation.Univariate linear regression analyses were performed to assess the association between practice size and area deprivation (Index of Multiple Deprivation), with positive response rates per GP practice. The impact of COVID-19 isolation policies was assessed visually by comparing positive response rates across different restriction phases. Results: Of the 13 814 invited participants, 12 816 (93%) did not respond. Of the 998 (7%) who responded, 690 (69%) were willing to participate (positive response), while 308 (31%) declined (negative response). Of the 308 negative responders, 209 provided a reason for not being willing or able to participate. The most frequently cited reason was the requirement to use a smartphone (40%), with 33% reporting they did not have a smartphone or internet access and 7% stating that they were unable or willing to use one. There was no association between response rate and COVID-19 restrictions on public life. Conclusions: In deprived areas, most people invited to participate in a dementia prevention study via their GP practice did not respond. Smartphone use emerged as a barrier to participation in this population. Our results suggest that major efforts are needed to reduce participation bias, increase generalisability of study results and address health inequalities in preventive interventions. Trial registration number: ISRCTN15986016.