Stroke, either ischemic stroke or intracerebral hemorrhage (ICH), is the leading cause of disability and one of the leading causes of death in adults. 10,28,31 Patients with ICH are at higher risk of disability than those with ischemic stroke, inclusive of greater economic and health care burdens. Exhibiting in 10%-20% of all strokes, ICH has been associated with both noninfectious and infectious factors. Studies have shown that intravenous drug use-related systemic infections increase the risk of cerebral vascular infection and subsequent rupture of mycotic aneurysms in cerebral arterioles. 9,15,32 Among noninfectious factors, pathological changes in the cerebral arterioles, including proliferation and death of arteriolar smooth muscle cells and arteriolar ectasia with microaneurysm formation 31 in the cerebral arterioles, may subsequently lead to the rupture of arteriolar microaneurysms, causing ICH. 10,28,31 These noninfectious pathological changes can be triggered by some conventional risk factors for ICH, such as hypertension, diabetes, hyperlipidemia, and chronic kidney disease (CKD). 16,18,20,21,24 However, risk factors for 10%-25% of ICH patients remain unclear, especially in the younger population. 16,18,21,24 Studies have documented well the role of chronic inflammation in triggering arterial ectasia and microaneurysm formation in the coronary artery. 7,21,24 Studies have also associated ICH with similar chronic inflammatory abbreviatioNs CKD = chronic kidney disease; COM = chronic osteomyelitis; HR = hazard ratio; ICH = intracerebral hemorrhage; IR = incidence rate; IRR = incidence rate ratio; NHI = National Health Insurance; RA = rheumatoid arthritis; SLE = systemic lupus erythematosus; VZV = varicella-zoster virus. obJect Inflammation may provoke cerebral arteriolar ectasia, inducing microaneurysm formation and further promoting intracerebral hemorrhage (ICH). Chronic osteomyelitis (COM) is an inflammatory disorder for which study of its role in ICH is lacking. This study explored whether COM increases the risk of ICH. methods From Taiwan national insurance inpatient claims, 22,052 patients who were newly diagnosed with COM between 1997 and 2010 were identified; 88,207 age and sex frequency-matched subjects without COM were selected at random for comparison. Risks of ICH associated with COM and comorbidities, including hypertension, diabetes, hyperlipidemia, chronic kidney disease, and drug abuse, were assessed by the end of 2010. results The incidence of ICH was 1.68 times higher in the COM cohort than in the comparison cohort, with an adjusted hazard ratio (HR) of 1.50 (95% CI 1.29-1.74) estimated in the multivariable Cox model. Age-specific analysis showed that the HR of ICH for COM patients decreased with age, with an adjusted HR of 3.28 (95% CI 1.88-5.75) in the < 40-year age group, which declined to 1.11 (95% CI 0.88-1.40) in the elderly. The incidence of ICH increased with the severity of COM; for those with severe COM the adjusted HR was 4.42 (95% CI 3.31-5.89). For subjects without comorbi...