Opt-out of Stop Smoking Service referral via SMS: a controlled interrupted time series analysis

To evaluate the impact of opt-out and self-referral (opt-in) invitations to a Stop Smoking Service (SSS) delivered via Short Message Service (SMS) by 14 general practices in Nottinghamshire, United Kingdom, on 28-day self-reported smoking abstinence.

Controlled and uncontrolled Interrupted Time series Analysis (ITSA) with cohort analysis.

A controlled ITSA of 13 practices (N = 145,170) that delivered opt-out invitations to 3,994 patients (59 % men; mean age 42.0 years) and cohort analysis. An uncontrolled ITSA of one practice (N = 19,100) that delivered self-referral invitations to 3,676 patients (56 % men; mean age 43.8 years).

Most patients did not opt out (91.7 %; 3,663/3,994), were contactable and confirmed smoking (52.4 %; 1,918/3,659). Of this group 21.7 % (417/1918) booked SSS appointments, and 7.1 % (137/1918) abstained from smoking (29 messages per abstinence). Most abstainers (73 %; 100/137) lived in high deprivation areas (IMD 1/2). Controlled ITSA indicated an immediate level increase of 13.1 in the weekly count of SSS patients who subsequently achieved abstinence (95 % CI: 5.0-21.1; p = 0.002). In the intervention month, 168 patients reported abstinence, 142 more than the pre-intervention mean of 25.6 (95 % prediction interval: 20.1-40.1). Uncontrolled ITSA indicated self-referral invitations did not change the count of SSS patients who became abstinent (0.22 patients per week; 95 % CI: 0.61-1.16; p = 0.601).

Proactive invitations to opt-out of SSS referral delivered via SMS by general practices were associated with a substantial increase in self-reported 28-day smoking abstinence. Self-referral invitations were not. The opt-out approach appears low-cost and scalable with potential to impact deprived populations.