Long-term circadian disruption shortens life span and dampens blood pressure diurnal rhythms in stroke-prone spontaneously hypertensive rats

Environmental cues such as light and timing of food intake influence molecular clocks that produce circadian rhythmicity of many biological functions. The master circadian clock is entrained by light input and synchronizes with peripheral clocks in every organ of the body. Careers that require rotating shift work schedules predispose workers to a constant desynchronization of these biological clocks and are associated with increased risk of cardiovascular disease. We used a stroke-prone spontaneously hypertensive rat model exposed to a known biological desynchronizer, chronic environmental circadian disruption (ECD), to test the hypothesis that it would accelerate the time to stroke onset. We then investigated whether time-restricted feeding could delay stroke onset and evaluated its usefulness as a countermeasure when combined with the constant disruption of the light cycle. We found that phase advancing of the light schedule accelerated stroke onset. Restricting food access time to 5 h/day regardless of lighting profoundly delayed stroke onset in both standard 12-h:12-h light/dark or ECD-lighting conditions compared with ad libitum feeding; however, acceleration by ECD versus control lighting conditions was still observed. Since hypertension is a precursor to stroke in this model, we assessed blood pressure in a small cohort longitudinally using telemetry. Mean daily systolic and diastolic blood pressure increased in a similar manner across rats in control and ECD conditions, thus hypertension was not grossly accelerated to cause earlier strokes. However, we observed intermittent dampening of rhythms after each shift of the light cycle reminiscent of a relapsing-remitting nondipping state. Our results suggest that constant disruption of environmental rhythms may be associated with an increased risk of cardiovascular complications in the presence of cardiovascular risk factors.