The goal of this clinical trial is to study whether a Cognitive Behavioural Therapy for Insomnia (CBT-I) group led by laypersons serves as an effective tool for alleviating insomnia in older Chinese adults in Hong Kong. The main questions it aims to answer are: 1) Can the group improve subjective sleep quality? 2) What is the feasibility and acceptability of the group? Researchers will compare the intervention group with a control group. Participants will either join the intervention group or receive a self-help booklet, depending on their assignment. Both groups will complete two questionnaires over a four-week period: Baseline and Week-4 data.