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Association of salivary cortisol with chronomics of 24 hours ambulatory blood pressure/heart rate among night shift workers

Recent studies indicate a circadian rhythm in blood pressure and heart rate and its association with various neurotransmitters. In the present study, we examine the circadian nature of blood pressure/heart rate and salivary cortisol in night shift workers and whether these circadian changes produced by night shifts are reversible. Sixteen healthy nurses of both genders, aged 20-40 years, performing day and night shift duties, were randomly selected out of 22 who volunteered for this study. Ambulatory blood pressure monitoring was done in all the subjects and salivary cortisol levels were analyzed during both day and night shift duties. There were clinically significant changes in the Acrophase of blood pressure and cortisol levels, indicating ecphasia (odd timing of systolic blood pressure) individually during night as well as day shifts. However, this pattern was statistically not significant. A reverse pattern of Acrophase was observed in 8 out of 16 subjects when they were posted on day shift. No significant change was found in midline estimating statistics of rhythm (MESOR) of blood pressure values. Changes in Double amplitude (Predictable change) were observed in 8 subjects during night shifts as well as in 7 subjects during day shifts. However, the pattern was not similar and night workers had an altered circadian pattern in the night as well as during day shifts. Changes in Double amplitude, Acrophase and Salivary cortisol were found during night as well as day shifts but these changes were not statistically significant (p > 0.05) due to incomplete recovery during day shifts (changes again seen when they came back to day shifts). Salivary cortisol levels were lowest in early morning, increased at midnight and further increased in the afternoon during night shifts along with ecphasia. It is possible that nurses working the night shift felt more tired due to the altered circadian cycle.

Variations in 7‐day/24‐h circadian pattern of ambulatory blood pressure and heart rate of type 2 diabetes patients

Diabetes has profound consequences on the cardiovascular system leading to cardiovascular morbidity and mortality in diabetic patients. Blood pressure (BP) has a characteristic and reproducible circadian pattern, with high values during the day and low values at night. A 7‐day timed analysis of BP through ambulatory blood pressure monitoring has been used not only to diagnose day and night dipping patterns of blood pressure, but also to measure day‐to‐day variability and the circadian hyper‐amplitude‐tension, a condition in which excessive circadian BP amplitude precedes the chronic established hypertension. Our objective was to assess the 7‐day/24‐h circadian pattern of BP and heart rate in diabetic patients, as it could be helpful in the diagnosis and prevention of cardiovascular morbidity.

Associations of Circadian Disruption of Sleep and Nutritional Factors with Risk of Cancer

Background: Daily entrainment of the human circadian clock is important for good human health. In previous studies, shift work has been linked to higher risk of chronic diseases, including certain types of cancers. Exposure to light at night suppresses the physiologic production of melatonin, a hormone that has antiproliferative effects on intestinal cancers. In the present review, we examine the available evidence on sleep disruption, changes in nutrient intake and nutritional factors and risk of cancers. Methods: Internet search of PubMed and discussion with colleagues. Results: Recent studies indicate that night shift work appears to have independent influence on the function of the endocrine system, gastrointestinal tract and circadian brain function. Sleep disruption enhances cortisol secretion and ghrelin release from the stomach and decreases melatonin and leptin which interfere with functioning of beta cells of pancreas. Apart from biological dysfunctions, behavioral changes, increased intake of refined carbohydrates, w-6 fats and low w-3 fats, physical inactivity, excess of tobacco and alcoholism appear to be common among night shift workers. Leptin signals the brain to feel satiety whereas ghrelin, produced in the stomach, signals hunger. Recent studies also indicate that sleep-deprived individuals with hormonal changes have greater cravings for sweet and fatty foods. Apart from this, stress hormone cortisol, which increases with sleep deprivation also contribute to hunger. In addition to altered hormone levels, late night awakening provides greater opportunity to eat, smoke and drink alcohol and eating often includes high-caloric foods. Epidemiological studies indicate that sleep disruption may be associated with obesity and other chronic diseases including cancers. Since electric light at night has adverse effects among night shift workers compared to day shift workers, it has been proposed that a portion of the high and rising risk of breast and prostate cancer worldwide may be because of night shift work. The suppression of melatonin by exposure to light at night may be one reason for the higher rates of breast, prostate and colorectal cancers in the developed world. Suppression of nocturnal melatonin by exposure to light at night results in lack of protection by melatonin on cancer cell receptor sites which allows the uptake of linoleic acid (LA) which in turn enhances the growth of cancer cells. Melatonin is a protective, oncostatic hormone and strong antioxidant having evolved in all plants and animals over the millennia. It is possible that rotating night shift at least three nights per month for 15 or more years may increase the risk of colorectal cancer and other cancers. Conclusions: Experimental evidence and limited human evidence allowed the International Agency for Research on Cancer (IARC) to classify circadian disruption of sleep, as a probable human carcinogen, group 2A. Behavioral changes, intake of fast foods, physical inactivity, excess of tobacco and alcoholism are common among night shift workers which may also apart from deficiency of melatonin.

155 CIRCADIAN PATTERN OF BLOOD PRESSURE AND HEART RATE IN ROTATING NIGHT SHIFT AND DAY SHIFT WORKERS

Background and Objectives: Shift work is known to cause circadian disruption of sleep leading to cardiovascular diseases (CVDs). We measured the circadian pattern of BP/HR in rotating night shift and day shift nursing professionals whether the changes in circadian pattern produced by rotating night shift are reversible. Subjects and Methods: We randomly recruited14 healthy nurses to perform day and night shift and another 14 nurses volunteer to perform day shift as controls (aged 20-40 years). Circadian pattern of BP/HR were evaluated by ambulatory BP monitors for (24 hours) in each subject in different shifts. Results: Night shift workers showed altered circadian pattern of double amplitude (predictable change) (SBP = 27.36 ± 18.83; DBP = 19.50 ± 12.78 of Night shift and SBP = 42.98 ± 20.75; DBP = 29.19 ± 13.48 of Day shift) when subjects went back to the day shift (SBP = p<0.04, DBP<0.02). A highly significant pattern of (SBP = 42.98 ± 20.75; DBP = 29.19 ± 13.48 of Day shift and SBP = 22.83 ± 10.99; DBP = 17.10 ± 6.83 of Controls) (SBP = p < 0.005, DBP = 0.006) of double amplitude was found between day shift and controls. Acrophase pattern (of individual subjects) was clinically significant in different shifts with controls. Significant changes were not found in MESOR values (p > 0.05). Conclusion: Alterations in Acrophase were persistent during night as well as day shift due to incomplete recovery and ecphasia (odd timing of blood pressure) was very common among night shift workers caused by internal desynchrononization.