In the stratosphere, reactive nitrogen species, including nitrogen oxides (NO and NO2, collectively NOx) are produced through the oxidation of nitrous oxide (N2O) and are closely linked with stratospheric ozone (O3) through catalytic loss processes. Interannual variability of nitrogen species and O3 are strongly influenced by the stratospheric quasi-biennial oscillation (QBO) in the tropical stratosphere. In this study, we examine variability of nitrogen species, and their links with O3, using over 10 years of satellite measurements from the Optical Spectrograph and InfraRed Imaging System (OSIRIS) instrument onboard the Odin spacecraft, together with the Aura Microwave Limb Sounder (MLS). We furthermore compare observations with simulations from the Whole Atmosphere Community Climate Model (WACCM4) global chemistry-climate model. Simulations of nitrogen species from WACCM4 enable a comprehensive analysis of the reactive nitrogen budget and variations linked to the QBO, and we find good agreement with observations. The model also shows evidence for coherent changes in the lower stratosphere associated with El Nino - Southern Oscillation (ENSO).