BACKGROUND:The number of hip fracture patients with dementia is increasing with an aging population,posing challenges for surgical treatment. OBJECTIVE:To determine the effect of dementia on postoperative complications in older patients with hip fractures. METHODS:Patients aged over 60 years old with hip fractures from 2000 to 2019 at Chinese PLA General Hospital were included.Dementia patients with a preexisting diagnosis of dementia at admission were identified.Each dementia patient was matched,for age±5 years,gender,and fracture type with 10 non-dementia patients.The differences in postoperative complications were compared between the two groups,including pneumonia,respiratory failure,gastrointestinal bleeding,urinary tract infection,surgical site infection,deep venous thrombosis,pulmonary embolism,angina pectoris,arrhythmia,heart failure,myocardial infarction,stroke,and death.The impact of dementia on major complications was evaluated using multivariate conditional logistic regression. RESULTS AND CONCLUSION:A total of 2 887 patients were included,of whom 125(4.3%)were dementia patients and matched with 1 243 non-dementia patients.The average age of dementia patients was(80.6±7.4)years;64.8%were female;53.6%were intertrochanteric fractures,and 46.4%were femoral neck fractures.Major complications occurred in 25(20.0%)patients with dementia and 123(9.9%)patients without dementia(P<0.01).The risk of major complications was 200.0 per 1 000 persons(95%CI,139.3-278.6)in dementia patients and 99.0 per 1 000 persons(95%CI,83.6-116.9)in non-dementia patients.Multivariate conditional logistic regression showed that a 2-fold risk of major postoperative complications after hip fracture surgery was found in dementia patients than in those without dementia(adjusted OR,2.11;95%CI,1.08-4.10).The results show that dementia is an independent risk factor for postoperative complications in elderly patients with hip fractures.Appropriate preoperative risk assessment and corresponding preventive and therapeutic measures should be given to this vulnerable population to mitigate postoperative complications.