OBJECTIVES: Patients with Type 1 Diabetes (T1D), have an immune system with a lower ability to respond to infectionStudies have shown that RAS-modifying medications (angiotensin converting enzyme [ACE] inhibitors and angiotensin receptor blockers [ARBs]) may reduce the risk for pulmonary infections. The aim of this study was to assess the impact of T1D and RAS therapy on pulmonary complications in patients with hypertension (HTN). METHODS: A retrospective analysis was conducted using claims data from a US commercial insurance company. The study groups consisted of patients taking either: ACE inhibitors, ARBs, or control (diuretics or calcium-channel blockers). Hazard ratios (HR) were estimated using Cox analyses to determine the impact of ACE inhibitors and ARBs on incidence of pulmonary complications controlled for diagnosis of T1D as a risk factor. The event included influenza, pneumonia, tuberculosis (TB), and Streptococcal sore throat (SSR). Initial drug model tested whether the risk of the events is impacted if the patient started with ACE inhibitors or ARBs while duration model tested whether everyday use of the medications delays the events. RESULTS: A total of 11,602 T1D patients and 154,083 non-diabetic patients using HTN drugs were identified. In initial drug model, T1D patients were at increased risk for influenza (HR=1.171, p<.0001) and pneumonia (HR=1.612, p<0.0001). Duration model showed that T1D patients were associated with increased risk of influenza (HR=1.235, p=0.0005), pneumonia (HR=1.680, p<.0001), and SSR (HR=1.223, p=0.0442). Patients treated with ACE inhibitors had lower incidence of pneumonia by 17% (HR =0.829, p<.0001) and TB by 30% (HR=0.698, p=0.0343), and ARBs exhibited a lower risk of pneumonia by 13% (HR=0.865, p<.0001) compared to control drugs. Duration model exhibited similar trends for each drug class. CONCLUSIONS: T1D was associated with increased risk of influenza and pneumonia. The use of RAS-modifying medications reduced the risk and delays onset of the diseases.