Night shift workers have a higher risk of developing atrial fibrillation (AF), new research has concluded.
In what is the first study to examine the links between night shift work and AF, researchers in China and the USA analysed data from 283,657 people in the UK Biobank database.
They found that the longer and more frequently that people worked night shifts, the greater their risk of AF. Night shift work was also linked to an increased risk of heart disease, but not to stroke or heart failure, they write in the European Heart Journal.
Professor Yingli Lu, of Shanghai Ninth People’s Hospital and Shanghai JiaoTong University School of Medicine, Shanghai, China, and Professor Lu Qi, of Tulane University School of Public Health and Tropical Medicine, New Orleans, USA, evaluated the overall genetic risk on the basis of 166 genetic variations known to be associated with the condition.
They found the genetic risk levels did not affect the link between working night shifts and AF risk, regardless of whether participants had a low, medium or high genetic risk.
Professor Lu said: “Although a study like this cannot show a causal link between night shifts and atrial fibrillation and heart disease, our results suggest that current and lifetime night shift work may increase the risk of these conditions.
“Our findings have public health implications for preventing atrial fibrillation. They suggest that reducing both the frequency and the duration of night shift work may be beneficial for the health of the heart and blood vessels.”
The study included 286,353 people, of whom 283,657 of did not have AF when they enrolled in UK Biobank, and 276,009 did not have heart failure or stroke.
Information on genetic variants was available for 193,819 participants without AF, and in 2015 75,391 of them answered in-depth questions about their lifetime of employment.
Among those who did not have heart disease and stroke when they joined the study, 73,986 provided information on their employment history. During an average follow-up time of over 10 years, there were 5,777 AF cases.
The researchers adjusted their analyses for factors that could affect the results and found people who worked night shifts on a usual or permanent basis had a 12% increased risk of AF compared to people who only worked during the day.
The risk increased to 18% after 10 or more years for those who had a lifetime duration of night shifts. Among people who worked an average of three to eight night shifts a month for 10 years or more, the risk of AF increased to 22% compared to day shift workers.
Those who worked night shifts, or had done so for 10 or more years, or who worked a lifetime of three to eight night shifts a month, had an increased risk of coronary heart disease by 22%, 37% and 35% respectively compared to daytime workers.
Professor Qi said: “There were two more interesting findings. We found that women were more susceptible to atrial fibrillation than men when working night shifts for more than 10 years. Their risk increased significantly by 64% compared to day workers.
“People reporting an ideal amount of physical activity of 150 minutes a week or more of moderate intensity, 75 minutes a week or more of vigorous intensity, or an equivalent combination, had a lower risk of atrial fibrillation than those with non-ideal physical activity when exposed to a lifetime of night shift work. Thus, women and less physically active people may benefit particularly from a reduction in night shift work.”
Although the numbers examined in the UK Biobank were high, the authors highlight some limitations, including the fact that most participants were white British, making it difficult to generalise the findings to other ethnic groups.
Prof Lu added: “We plan to analyse the association between night shift work and atrial fibrillation in different groups of people. This may strengthen the reliability of these results and serve as a warning to groups working in certain types of occupations to get their hearts checked early if they feel any pain or discomfort in their chests.”
Wang n et al. Long-term night shift work is associated with the risk of atrial fibrillation and coronary heart disease. European Heart Journal 16 August 2021; doi:10.1093/eurheartj/ehab505
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