Key result
Night shifts show no significant link to altered circadian BP or HR versus day shifts.
Why the study?
The circadian nature of blood pressure, heart rate, and salivary cortisol in night shift workers and the reversibility of these changes were not well understood.
Does night shift work alter the circadian rhythm of blood pressure, heart rate, and salivary cortisol in healthy nurses?
Observational (n=16)
No
Does night shift work alter the circadian rhythm of blood pressure, heart rate, and salivary cortisol in healthy nurses?
Absolute Event Rate: 114.46% vs 113.31%
p-value: p=0.30
Night shift work induces alterations in the circadian rhythms of blood pressure and salivary cortisol among healthy nurses, though these changes were not statistically significant in this small sample.
Observable but non-significant circadian shifts in night-shift nurses merit caution; leaves open confirmation in larger prospective studies.
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.
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Anjum et al. (2011) conducted an observational in Healthy night shift workers (n=16). Night shift work vs. Day shift work was evaluated on MESOR of systolic blood pressure (p=0.30). Night shift work induced clinically observable but statistically non-significant alterations in the circadian patterns of blood pressure, heart rate, and salivary cortisol compared to day shifts.
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