Orthostatic blood pressure reactions and resting heart rate in relation to lung function - the Swedish CArdioPulmonary bioImage Study (SCAPIS)

Background There is a well-known comorbidity between chronic obstructive pulmonary disease (COPD) and coronary artery disease (CAD) which is only partially explained by common risk factors. Markers of cardiovascular autonomic dysfunction (CVAD), such as orthostatic hypotension and increased resting heart rate, are strongly associated with CAD. The autonomic nervous system also innervates the airways, and several studies have shown an association between autonomic dysfunction and COPD. However, less is known about whether CVAD and impairment of respiratory capacity are related in the population. We thus aimed to assess the relationship between markers of subtle CVAD and lung function in middle-aged subjects. Methods In this cross-sectional study, we analysed data from CVAD assessment (orthostatic blood pressure and heart rate measurements) and pulmonary function tests from 5886 individuals from the Swedish CArdioPulmonary bioImage Study (SCAPIS). Subjects were middle aged and randomly selected from the Swedish population. Linear regression models and ANOVA analyses were used to relate orthostatic blood pressure and resting heart rate to lung function parameters (forced vital capacity (FVC), forced expiratory volume in one second (FEV 1 ), FEV 1 /FVC-ratio, diffusion capacity for carbon monoxide (D LCO ), respiratory resistance at 5 Hz (R5), respiratory resistance at 20 Hz (R20), decrease in resistance from R5 to R20 (R5-R20), reactance in distal airways (X5), resonant frequency (Fres) and reactance area (AX)). Results Increasing systolic orthostatic blood pressure, decreasing diastolic orthostatic blood pressure, and increased resting heart rate associated with lower FVC (all p < 0.001) and FEV 1 ( p = 0.001; p = 0.005; p < 0.001, respectively) in models including age, sex and height. Apart from diastolic orthostatic blood pressure and FEV 1 , all relationships remained significant after adjustment for possible confounders. Increased resting heart rate was associated with reduced D LCO ( p < 0.001). Conclusions Increasing systolic orthostatic blood pressure, decreasing diastolic orthostatic blood pressure, and increased resting heart rate are associated with lower lung function, after adjustments for age, sex and height. These finding indicates associations between signs of cardiovascular autonomic dysfunction and lower lung function in the general population. However, the observed differences in lung function were small and the clinical application is unclear.