Inclusion Criteria:  Aged ≥65 years; T2D with suboptimal glycemic control defined as HbA1c 7.5-10%; Chinese ethnicity; Comorbid with insomnia having ISI score >14; Able and willing to give informed written consen  Exclusion criteria:  Cognitive impairment (HK-MoCA score of ≤22); Depression (GDS-15 score >8) and other psychiatric disorders e.g. generalized anxiety disorder, restless leg syndrome, schizophrenia to be elucidated by history from research nurse and questionnaires; OSA as defined as apnoea-hypopnoea index (AHI) ≥15 events per night; Benign prostatic hypertrophy by history and/or elevated PSA and any other chronic medical condition that is likely to affect sleep e.g. chronic pain; Concurrent use of hypnotic drugs, psychotic medications and any drugs that are known to affect sleep; Cerebrovascular accidents, vascular dementia, or any condition that are known to affect cognitive function; Shift workers; Haemoglobinopathies, renal failure, need of regular blood transfusion or any other conditions which will affect the validity of HbA1c in measurement of glycemia; Any condition, as judged by the investigators, as ineligible to participate in this study.