Sleep disruption from inhalation of biomass smoke: a basis for coincident hypertension?

BACKGROUND: Exposure to air pollution including contemporary sources like wildland fire smoke worsens cardiovascular outcomes. Although several mechanisms for these effects have been postulated, one underexplored impact of inhaled air pollution that may mediate adverse health outcomes is sleep disruption, which is an independent risk factor for cardiovascular morbidity and a trigger of multiple biological pathways linked to disease. The purpose of this study was to determine whether cardiovascular responses to air pollution, especially excursions in blood pressure, are associated with contemporaneous changes in sleep status. Three-month old male and female Sprague Dawley rats were implanted with radiotelemetry devices that simultaneously measured aortic blood pressure and the electroencephalogram (EEG), which was used to quantify sleep quality and depth. Heart rate variability (HRV), an indirect measure of autonomic tone, and blood pressure variability (BPV) were assessed from the blood pressure signal. Rats were monitored before, during and after a single 1-hour whole body inhalation exposure to filtered air or tube furnace-generated eucalyptus smoke (632-904 µg/m3 fine particulate matter (PM2.5; ≤ 2.5 microns in aerodynamic diameter)), a key wildland fire-linked air pollution source.

RESULTS: Smoke exposure caused increases in heart rate, blood pressure, BPV, and HRV markers of sympathetic tone and concomitant disruption in several sleep parameters including slow-wave and paradoxical sleep, and wake duration to varying degrees in male and female rats relative to sex-matched filtered air controls during exposure.After exposure, smoke caused decreases in cardiovascular function and sympathetic tone that again varied by sex, although both males and females had rebound increases in sleep drive. Finally, although there were some minor sex differences, the cardiovascular and sleep responses in the smoke groups were largely more strongly correlated with one another and with HRV markers of sympathetic tone relative to responses in the respective filtered air groups.

CONCLUSIONS: These findings suggest that some of the cardiovascular responses to air pollution, including hypertension, may be related to perturbations in sleep and associated changes in autonomic tone.