Shiftwork-Mediated Disruptions of Circadian Rhythms and Sleep Homeostasis Cause Serious Health Problems

Abstract

Shiftwork became common during the last few decades with the growing demands of human life. Despite the social inactivity and irregularity in habits, working in continuous irregular shifts causes serious health issues including sleep disorders, psychiatric disorders, cancer, and metabolic disorders. These health problems arise due to the disruption in circadian clock system, which is associated with alterations in genetic expressions. Alteration in clock controlling genes further affects genes linked with disorders including major depression disorder, bipolar disorder, phase delay and phase advance sleep syndromes, breast cancer, and colon cancer. A diverse research work is needed focusing on broad spectrum changes caused by jet lag in brain and neuronal system. This review is an attempt to motivate the researchers to conduct advanced studies in this area to identify the risk factors and mechanisms. Its goal is extended to make the shift workers aware about the risks associated with shiftwork.

Figure 1

The abnormalities associated with shiftwork. (1) Shiftwork primarily affects the circadian clock and leads to several disruptions and disorders. (2) Disruption in circadian clock further affects the circadian system and alters important gene expressions which play an important role in maintaining normal body functions. (3) BMAL1 and CLOCK genes are the key factors that control circadian rhythms. Any alteration in these groups of genes further alters the genetic expression of genes (Per 1–3 and Cry 1/2) involved in clock maintenance. Other factors and proteins which play a major role in circadian rhythm are RORs, REV-ERBs, CK1δ, CK1ε, AMPK, FBXL3 and βTRC. (4) Shiftwork either directly or through circadian system alterations may cause severe psychiatric disorders including major depression, anxiety, and mood disorders. (5) Due to exposure to light irregularly, shiftwork enhances the chances of breast cancer. Breast cancer development is promoted by sleep disruptions, circadian system imbalances, and dietary conditions. (6) Sleep disorders and disrupted sleep is another condition developed by shiftwork. (7) This disruption in sleep affects the metabolism and causes metabolic disorders including obesity.

Figure 2

All disorders that could possibly be caused by shiftwork.