Inflammatory processes may trigger neuroinflammation and cerebrovascular dysfunctions, further provoking dementia. The role of chronic osteomyelitis (COM), a disorder characterized by persistent inflammation, in dementia development has not been fully explored. This study investigates whether COM increases the risk of dementia. Taiwanese National Health Insurance (NHI) inpatient claims were used to identify 17,238 patients newly diagnosed with COM from 2000 to 2008, and 68,944 age- and gender-matched patients without COM were randomly selected for comparison. Risks of dementia associated with COM and comorbidities, including hypertension, diabetes, stroke, hyperlipidemia, and depression, were evaluated using data from the end of 2011. Dementia risk was 1.6-fold higher (95% confidence interval [CI]: 1.4-1.83) in the COM cohort than in the control group, calculated using the multivariable Cox model. Age-specific analysis indicated that the adjusted hazard ratios (aHRs) of dementia for COM patients decreased with age, with an aHR of 3.65 (95% CI: 1.5-8.9) for patients <55 years old, which gradually decreased to 1.43 (95% CI: 1.23-1.66) for patients ≥ 70 years old. Dementia risk increased with COM severity, with an aHR of 5.48 (95% CI: 4.43-6.79) for patients with severe COM. For those without comorbidities, dementia risk was 1.73-fold (95% CI: 1.37-2.17) higher in the COM cohort than in the control group. This study is the first to find that COM is an inflammatory disorder associated with an increased risk of dementia, particularly among younger people.