Note: RCT = randomized controlled trial; ACS = acute coronary syndrome;
STEMI = ST-elevation myocardial infarction; PCI = percutaneous cardiac
intervention; CBT = cognitive behavioral therapy; SS = sleep seminar;
TCC = Tai Chi CHIH
Limitations
As many as three clinical trials from the past five years
were discovered to evaluate the impact of working in a shift on
cardiovascular diseases. However, two studies did not assess the job
characteristics in the shift, or the intensity and stress included that
may heighten its impact on the risk of cardiovascular diseases.
Consequently, the exact elevation in risk imposed in working in a shift
could not be thoroughly
estimated.
DISCUSSION
The internal system, or known as the circadian rhythm, is accountable
for well-ordered roles of the immunological and metabolic systems. The
release of cortisol is correlated with the moderation of the circadian
rhythm; cortisol begins to increase several hours after sleep, peaked in
early in the morning and in the hours of awakening, promoting the body
to shift from biological night time to biological daytime. Any sleep
disturbances influence the release of circadian; it rises in
wakefulness, insomnia, or reduced sleep. Likewise, working in shift
disturbs the regular pattern of release, induces lethargy, and causes
the release of epinephrine and norepinephrine, sequentially affecting
the variability of the heartbeat, heart rate, and blood pressure.
Melatonin begins to rise after nightfall, peaked by midnight, then
progressively declines in the following half. Working conditions with
rotating shift provoked abnormality in melatonin concentration [14].
Melatonin concentration is related to the occurrence of cardiovascular
events. It was found to be decreased in coronary artery diseases (CAD)
patients. The lower the concentration of melatonin, the more the risk of
cardiovascular events, such as myocardial infarction (MI). It confirms
that the severity of cardiovascular diseases was inversely proportional
to melatonin levels [15]. Several cardiovascular variables were
modified in a diurnal pattern with the circadian pattern, involving
blood pressure, heart rate, and the activity of fibrinogen [16]; and
also platelet activity, endothelial function, vascular tone, and lipid
metabolism [17], which partially reveals high occurrence of
cardiovascular events in the morning following the circadian
rhythm [17]. In 2011, Sheer at al. explained the relationship
between the activity of platelets with circadian rhythm [18], which
was seen to be most eminent in early daylight [19]. These variations
occur by the intrinsic circadian rhythm; hence, peripheral oscillators
reflect the circadian rhythm and are influenced by circadian disruption.
Added factor in predicting cardiovascular diseases’ risk is the
concentration of inflammatory markers, such as interleukins [20].