The goal of this clinical trial is to learn if 4-week xylitol gum intervention works to promote smoking cessation in daily smokers. It will also learn about the feasibility and acceptability of using xylitol gum. The main questions it aims to answer are:

（1）Does xylitol gum help to reduce cigarette consumption and promote smoking cessation?

Researchers will compare 4-week xylitol gum intervention to the brief advice to see if xylitol gum works to promote smoking cessation.

Participants in the intervention group will receive a 3-month behavioral intervention comprising a 4-week xylitol gum aligned with 12 weeks of instant reminder message support.

This study aims to evaluate the feasibility, acceptability, and preliminary effectiveness of a proactive smoking cessation intervention using xylitol chewing gum. Eligible participants will be Hong Kong residents aged ≥18 years who (1) have smoked at least one cigarette per day in the past 3 months; (2) can communicate in Cantonese (including reading Chinese); (3) express an intention to quit or reduce smoking; (4) are able to use instant messaging tools (e.g., WhatsApp); and (5) regularly chew gum or are willing to use chewing gum for smoking reduction.

A total of 134 participants will be recruited from community settings, including public housing estates across Hong Kong's 18 districts, community and university smoking hotspots, referrals from other smoking cessation programmes, and social media promotions (Facebook and Instagram). The study will adopt a hybrid type I effectiveness-implementation design. Participants will be followed up at 1, 3, and 6 months post-enrolment via telephone, following CONSORT guidelines, to assess cigarette reduction and cessation outcomes.

All participants will receive brief smoking cessation advice at baseline using the AWARD model (Ask/Assess, Warn, Advise, Refer, and Do-it-again), accompanied by a health warning leaflet and a smoking cessation information booklet.

Interventions are as follows:

Chewing gum group (intervention): Participants will receive 4 packs of xylitol gum at baseline and up to 24 packs throughout the 12-week intervention. Approximately 24 reminder messages (two per week), developed based on the Love and Care Approach framework, will be delivered via instant messaging to reinforce motivation and adherence.

Unassisted quitting group (control): Participants will receive brief advice only at baseline.

To explore user experience and acceptability, semi-structured qualitative interviews will be conducted with 20 intervention-group participants to understand their perceptions and experiences with xylitol gum use.

The primary outcome is biochemically validated smoking abstinence at 6 months, defined as exhaled carbon monoxide <4 ppm and salivary cotinine <30 ng/mL.

Inclusion Criteria:

• Residents of Hong Kong aged 18 or above who smoke at least 1 cigarette per day over the past 3 months
• Have the habit of chewing gum or are willing to use chewing gum
• Can communicate in Cantonese (including reading Chinese)
• Express an intention to quit or reduce smoking
• Capable of using instant messaging tools (e.g., WhatsApp, WeChat) for communication

Exclusion Criteria:

• Have communication barriers (either physical or cognitive)
• Currently participating in other smoking cessation programs or services