Brisk Walking Training Compared with Cognitive Behavioral Therapy for the Treatment of Chronic Primary Insomnia in People Aged 60 Years or Above: a Randomized, Partially Blinded, Non-inferiority Trial

Inclusion Criteria: 1. Aged ≥60 years; 2. Ethnic Chinese; able to read, write and speak Cantonese 3. Having a Hong Kong ID; 4. Willing to wear an accelerometer on the wrist for a week to assess sleep parameters at T0, T1, and T2. 5. Score ≥10 in the Insomnia Severity Index (ISI) (presence of insomnia) 6. Experiencing any one of the following symptoms for ≥3 days per week 1. Difficulty initiating sleep; OR 2. Difficulty maintaining sleep; OR 3. Early-morning awakening with inability to return to sleep Exclusion Criteria: 1. Score ≥1 in the Chinese version of the Physical Activity Readiness Questionnaire (PAR-Q); 2. Currently regularly practicing a moderate-intensity PA program such as brisk walking or Tai Chi (≥3 times a week, ≥30 minutes/session); 3. Currently receiving or scheduled to receive CBT-I during the study period; 4. Score ≤16 in the validated telephone version of the Cantonese Mini-Mental State Examination (T-CMMSE). 5. Working nightshifts and unable/unwilling to discontinue such work pattern; 6. Having a diagnosis of a major depressive disorder, anxiety disorders or other severe mental disorder (bipolar disorders, psychosis). Those with mild depression or anxiety disorders will not be excluded; 7. Use of antidepressant or antipsychotic medication or under treatment of other serious diseases (e.g., cancer chemotherapy) known to affect sleep; 8. Presence of any serious chronic diseases which affect sleep (e.g., cancer, autoimmune diseases). 9. Having a serious somatic condition preventing the participation of brisk walking training/CBT-I.