IntroductionEvidence on long-term associations between COVID-19 and risks of multi-organ complications and mortality in older population is limited. This study evaluates these associations.Research design and methodsThe cohorts included patients aged ≥60 year diagnosed with COVID-19 infection (cases), between 16 March 2020 and 31 May 2021 from the UK Biobank (UKB cohort, n = 11 330); and between 01 April 2020 and 31 May 2022 from the electronic health records in Hong Kong (HK cohort, n = 213 618). Each patient was randomly matched with up to 10 individuals without COVID-19 infection based on age and sex (UKB, n = 325 812; HK, n = 1 411 206) and were followed for up to 18 months until 31 August 2021 for UKB, and up to 28 months until 15 August 2022 for HK cohort. Caracteristics between cohorts were further adjusted with propensity score-based marginal mean weighting through stratification. For evaluating long-term association of COVID-19 with multi-organ disease complications and mortality after 21-days of diagnosis, Cox regression was employed.ResultOlder adults with COVID-19 were associated with a significantly higher risk of cardiovascular outcomes [major cardiovascular disease (stroke, heart failure and coronary heart disease): hazard ratio (UKB): 1.4 (95% Confidence interval: 1.2,1.7), HK:1.2 (95% CI: 1.1,1.3)]; myocardial infarction: HR (UKB): 1.8 (95% CI: 1.4,2.5), HK:1.2 (95% CI: 1.1,1.5)]; respiratory outcomes [interstitial lung disease: HR (UKB: 3.5 (95% CI: 2.6,4.7), HK:6.6 (95% CI: 2.1,21.2); chronic pulmonary disease: HR (UKB): 1.6 (95% CI: 1.2,2.1), HK:1.7 (95% CI: 1.4,2.1)]; neuropsychiatric outcomes [seizure: HR (UKB): 2.7 (95% CI: 1.7,4.2), HK:1.8 (95% CI: 1.4,2.3)]; and renal outcomes [acute kidney disease: HR (UKB): 1.4 (95% CI: 1.1,1.6), HK:1.7 (95% CI: 1.4,2.1)]; and all-cause mortality [HR (UKB): 4.8 (95% CI: 4.4,5.4), HK:2.7 (95% CI: 2.6,2.8)].ConclusionCOVID-19 is associated with long-term risks of multi-organ complications in older adults (aged ≥60). Infected patients in this age-group may benefit from appropriate monitoring of signs/symptoms for developing these complications.