Background Long-term cognitive problems are common among elderly patients after surgery, and it has been suggested that inhalation anaesthetics play a role in the development of dementia. This study aims to investigate the hypothesis that patients with dementia have been more exposed to surgery and inhalational anaesthetics than individuals without dementia. Methods Using 457 cases from a dementia-registry and 420 dementia-free controls, we performed a retrospective case-control study. The medical records were reviewed to determine exposure to anaesthesia occurring within a 20-year timeframe before the diagnosis or inclusion in the study. Data were analysed using multivariate logistic regression and propensity score analysis. Results Advanced age (70 years and older, with the highest risk in ages 80 to 84 years) and previous head trauma were risk factors for dementia. History of exposure to surgery with anaesthesia was a risk factor for dementia (OR = 2.23, 95% CI 1.66-3.00, P < 0.01). Exposure to inhalational anaesthetics with halogenated anaesthetics was associated with an increased risk of dementia, compared to no exposure to anaesthesia (OR = 2.47, 95% CI 1.17-5.22, P = 0.02). Exposure to regional anaesthesia was not significantly associated with increased risk of dementia (P=0.13). Conclusion In this 20-year retrospective case-control study, we found a potential association between dementia and prior anaesthesia. Exposure to general anaesthetics with halogenated anaesthetic gases was associated with an increased risk of dementia.