Abstract
Cardiovascular diseases are the top cause of mortality in the United States, and ischemic heart disease accounts for 16% of all deaths around the world. Modifiable risk factors such as diet and exercise have often been primary targets in addressing these conditions. However, mounting evidence suggests that environmental factors that disrupt physiological rhythms might contribute to the development of these diseases, as well as contribute to increasing other risk factors that are typically associated with cardiovascular disease. Exposure to light at night, transmeridian travel, and social jetlag disrupt endogenous circadian rhythms, which, in turn, alter carefully orchestrated bodily functioning, and elevate the risk of disease and injury. Research into how disrupted circadian rhythms affect physiology and behavior has begun to reveal the intricacies of how seemingly innocuous environmental and social factors have dramatic consequences on mammalian physiology and behavior. Despite the new focus on the importance of circadian rhythms, and how disrupted circadian rhythms contribute to cardiovascular diseases, many questions in this field remain unanswered. Further, neither time-of-day nor sex as a biological variable have been consistently and thoroughly taken into account in previous studies of circadian rhythm disruption and cardiovascular disease. In this review, we will first discuss biological rhythms and the master temporal regulator that controls these rhythms, focusing on the cardiovascular system, its rhythms, and the pathology associated with its disruption, while emphasizing the importance of the time-of-day as a variable that directly affects outcomes in controlled studies, and how temporal data will inform clinical practice and influence personalized medicine. Finally, we will discuss evidence supporting the existence of sex differences in cardiovascular function and outcomes following an injury, and highlight the need for consistent inclusion of both sexes in studies that aim to understand cardiovascular function and improve cardiovascular health.
Highlights
The occurrence and increased incidence of these maladaptive processes coincides with technological and societal advances that expose individuals to light ‘around the clock’. This is the case with night shift workers, whose activity pattern is typically misaligned with their internal clock, and who are often exposed to bright light during the night, further disrupting their biological rhythms
Circadian rhythms are present in all mammals and regulate many physiological processes
We have reviewed evidence detailing how this system is stringently regulated by circadian clocks, and how their disruption can have detrimental consequences on outcomes
Summary
Most organisms on Earth have an internal, organizational, timing system termed biological oscillators or ‘clocks’ These endogenous oscillators establish and maintain rhythms that allow organisms to anticipate and prepare for predictable events such as resource scarcity or darkness, with the goal of efficiently using energy, properly allocating resources, and optimally timing behaviors, including reproduction. These clocks drive circadian (having a period of ~24 h) rhythmicity in physiology and behavior and govern most biological processes. These circadian TTFLs regulate the activity of ~43% of all transcribed genes [36], which are themselves expressed in a circadian fashion in the various organs and cells
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
