Effects Of Photoperiodism On Daily Rhythms Of Blood Pressure And Heart Rate In Different Seasons Of The Year In The Arctic

Objective: To study the effect of the rhythm of natural light on circadian rhythms of blood pressure (BP) and heart rate (HR) in the Arctic. Design and method: Analysis of 24-hour BP monitoring was performed in 373 male patients with arterial hypertension (AH) stage II engaged in rotational shiftwork in the Arctic compared with the group of the same type of 144 patients living in moderate climate (Tyumen, 57 N) 93 randomly selected patients of the Northern group and 64 patients of the Tyumen group. Based on 24-hour ambulatory blood pressure monitoring chronobiological and standard parameters, daily BP profile, circadian BP and HR indices, percentage contribution value (PC), amplitude of a rhythm (RA), acrophase and BP MESOR in different seasons were analyzed. Results: In the conditions of Arctic shift work circadian BP and HR rhythms in patients with AH differed significantly compared with Tyumen patients regardless of season and were characterized by the absence of seasonality signs of BP and HR rhythms and the presence of inside desynchronosis of rhythms. Lack of natural light during the polar day and polar night leads to flattened HR and circadian BP in patients with AH in the Far North. The major differences were the loss of 24-hour period components and low-amplitude spectrum profile. Seasonal changes in the HR parameters were not significant in the comparison group versus northern group with a clear flattening of HR in the polar day period. In the main group of patients the worst condition for 24-hour BP profile was winter period (polar night) characterized by the peak flattening of circadian rhythms and the prevalence of high-frequency oscillations in the spectrum. Conclusions: In patients with AH in the conditions of Arctic shift work, formation of daily rhythm and absence of seasonality signs of HR and BP is associated with nature of work and climate factors, including natural light rhythm in the northern latitude.