Scientists talked about the effect of dirty air on the work of the heart

Prolonged exposure to polluted air can put strain on the autonomic nervous system that regulates the heart. The researchers found that when exposed to pollutants for longer than three hours, heart rate variability begins to decrease more noticeably. This was reported in the journal BMC Public Health.

Specialists from the University of Louisville analyzed the results of 27 previously published controlled trials involving 747 people. In total, the scientists reviewed 55 data sets. In the experiments, the volunteers were exposed to polluted air, after which the obtained indicators were compared with the results in filtered air conditions.

The duration of exposure ranged from 30 minutes to five hours. The scientists studied the effects of fine particles PM2.5 and PM10, ultrafine particles, ozone, nitrogen dioxide and several combinations of pollutants. Almost half of the analyzed data related to exposure to PM2.5 particles capable of penetrating deep into the respiratory tract.

The main indicator was heart rate variability, a change in the intervals between successive heart contractions. This parameter reflects how flexibly the cardiovascular system adapts to stress and signals from the autonomic nervous system. A decrease in variability may indicate a weakening of parasympathetic regulation and increased physiological stress.

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During the first three hours, exposure to polluted air was not accompanied by significant changes in the indicator. However, in studies with longer experiments, heart rate variability decreased more strongly. By five o'clock, the observed effect remained small, but became more pronounced compared to exposure lasting up to three hours.

According to the researchers, this reaction may be due to the fact that pollutants take time to trigger inflammatory processes, malfunction of the vascular endothelium and changes in autonomous reflexes. As a result, the activity of the parasympathetic nervous system may decrease, which is responsible, among other things, for restoring the body and regulating the heart rate.

At the same time, the authors emphasize that the study does not prove the existence of a universal three-hour threshold, after which polluted air necessarily damages the heart. The revealed pattern was obtained by comparing different experimental protocols, rather than by continuously monitoring the reaction of each individual. In addition, the researchers assessed an intermediate physiological indicator, rather than the frequency of heart attacks or other cardiovascular diseases.

The overall reliability of the evidence was assessed as low. Most of the included studies had a small sample — about 18 participants on average, and 41 of the 55 datasets related to exposures lasting less than three hours. The experiments also varied in the composition and concentration of pollutants, and the laboratory conditions did not fully reflect the situation on the street.

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Russian Minister of Health Mikhail Murashko said on July 31 that the risk of developing cancer, cardiovascular and endocrine diseases largely depends on a person's lifestyle. He recommended regular checkups, quitting smoking and drinking alcohol. The head of the Ministry of Health stressed that timely prevention and a healthy lifestyle help reduce the likelihood of developing many chronic diseases.