Most smoking patients continue to smoke (76.1%) after being discharged from hospitals. Post-discharge smoking cessation (SC) support is one of the most cost-effective treatments. Hospitalisation offers a teachable moment to motivate patients to engage in post-discharge intervention, particularly those suffering from smoking-related diseases. Behavioral and psychosocial support increases abstinence in patients. Current clinical guidelines in the US (USPSTF) and UK (NICE) recommend health care professionals to provide brief SC support to patients using a brief advice model such as the 5As (Ask, Assess, Advice, Assist, Arrange) and further motivational 5Rs interventions (Relevance, Risks, Rewards, Roadblocks, and Repetition) if needed for those not having quit attempts. A key trial found that providing discharged patients with such proactive and sustained care as free SC medication, telephone calls to promote quitting, and additional counselling through clinic referrals increased 6-months validated quitting. Trained patient navigators providing patients in hospital primary clinics with tailored individual advice with medication and counselling referrals were found to be effective at improving 12-months quitting. Previous trials also showed connecting community smokers or smokers who visited emergency departments to existing SC services increased validated quitting at 6-months. Recent advances in mobile phone technology allow incorporating such innovations to improve the cost-effectiveness of post-discharge smoking cessation services.

Mobile phones are increasingly used for monitoring and delivering personalised health treatments (mHealth). Regular text messaging was found to increased 6-months validated abstinence in general smokers, although the study was limited to pre-defined messages and interactions. A previous study reported an automated interactive voice response to be favored by patients and to increase abstinence. A text-based programme was tested in a Chinese population, and previous study found the delivery of interactive chat-based SC support via IM apps to be effective in increasing quitting. Chat-based SC interventions can provide real-time, personalised behavioral support and referrals to SC services. Mobile health is also part of the World Health Organization's strategies to combat smoking.

Leveraging the success of previous trials in inpatients and a chat-based trial using IM to deliver behavioral support to community smokers, This study proposes to refine the 5As cessation model by incorporating a mobile phone-based intervention for patients recently discharged from hospitals. Recent trials showed a mobile phone-delivered cessation intervention combined with SC medication service increased abstinence. Recent trials showed a mobile phone-delivered cessation intervention combined with SC medication service increased abstinence. Active referral of community smokers to smoking cessation services increases service use and quitting but smoking patients were not referred for sustained cessation service in hospitals in Hong Kong. The effect of mobile phone-based intervention with active referral to link discharged patients for standard smoking cessation service remains unclear. Therefore, This study proposes to enhance the general 5As brief advice model with interactive mobile phone-based intervention and active referral to community smoking cessation services for smoking patients discharged from hospitals in Hong Kong.