Long-Term Night Shift Work Associated With Higher COPD Risk

Long-term night shift work is associated with a higher risk of chronic obstructive pulmonary disease (COPD), according to a study published in BMC Medicine.

Although tobacco smoking is considered the most prevalent cause of COPD, the researchers explained that recent evidence indicates approximately half of COPD cases worldwide are caused by non–tobacco-related risk factors. Consequently, they chose to study whether long-term night shift work increased patients’ COPD risk.

This topic was of interest to them as evening, night, and rotating shifts have become more prevalent worldwide. The harmful health effects of night shifts have become a growing concern in recent decades as they can disrupt circadian rhythm, impair sleep quality, and affect work-life balance. The researchers noted that night shifts have already been associated with increased risks of cardiovascular diseases, infection susceptibility, metabolic disorders, and cancer.

In particular, night shift work's impact on circadian rhythm changes patients’ airway caliber, respiratory symptoms, airway resistance, mucus hypersecretion, and immune-inflammatory responses. Because of this, the researchers hypothesized that night shifts may result in airway damage and impaired lung function, ultimately contributing to the development of chronic airway diseases, like COPD.

Despite this connection, the relationships between long-term exposure to night shift work and COPD risk have not yet been addressed. Consequently, the researchers explored this relationship, as well as how genetic susceptibility affects it.

To do so, the researchers used a dataset from the UK Biobank, a large-scale prospective cohort study that included more than 500,000 adults from the UK between 2006 and 2010; the study focused on employed participants. Conversely, the researchers excluded participants with missing covariate data and those with COPD at baseline since the study was an analysis of incident COPD.

To conduct the study, the researchers obtained information on patients’ current and lifetime employment. They also constructed a weighted COPD-specific genetic risk score (GRS) and used Cox proportional hazard models to investigate associations between night shift work and COPD risk, along with their interaction with COPD-specific GRS.

Night shift | Image Credit: creative soul - stock.adobe.com

Initially, the researchers identified 287,073 employed participants from the UK Biobank. After eliminating those with missing data and COPD at baseline, the study population consisted of 277,059 participants, 133,063 of whom were men; the mean (SD) age was 52.71 (7.08) years.

The population was split up into 3 categories: “day workers,” “shift, but rarely/some night shifts,” and “usual/permanent night shifts.” Of the included participants, 82.83% were day workers, 13.37% worked some night shifts, and 3.80% worked permanent night shifts. The researchers noted that night shift workers were more likely to be younger males with higher body mass indexes (BMIs); they were also more likely to be current smokers with shorter sleep durations.

The researchers documented 6558 COPD incidents during a median of 12.87 years of follow-up. They concluded that both irregular (HR, 1.28; 95% CI, 1.20-1.37; P < .001) and permanent night shift work (HR, 1.49; 95% CI, 1.35-1.66; P < .001) were significantly related to a higher COPD risk. More specifically, the researchers associated participants with longer night shift durations, namely those who worked night shifts for 10 or more years, with a higher COPD risk (HR, 1.23; 95% CI, 1.03-1.46). They also found that the participants who undertook more than 8 night shifts per month had a higher COPD risk (HR, 1.41; 95% CI, 1.19-1.68).

Additionally, the researchers discovered an additive interaction between night shifts and genetic susceptibility in terms of COPD risk. They explained that each SD increment in GRS was associated with a 9% increase in COPD risk (HR, 1.09; 95% CI, 1.06-1.12). The researchers also observed significant joint effects between genetic risk and current work schedule, as the overall COPD incidence risk increased as both genetic risk and night work–related risk increased. Compared with day workers who had lower genetic risk, those with usual/permanent night shift work and high genetic risk had the highest COPD risk (HR, 1.90; 95% CI, 1.63-2.22).

The researchers acknowledged their study’s limitations, one being that the data on current and former employment history, along with some of the COPD incidence data, were assessed by self-report; this may have contributed to misclassification. Also, most of the participants included in the study were White, which limits the generalizability of their findings to other racial or ethnic groups. Despite these limitations, the researchers made suggestions on how to address the higher COPD risk in patients who work long-term night shifts.

“Our findings suggest that decreasing the frequency and duration of night shifts may offer a promising approach to mitigating respiratory disease incidence in night shift workers, particularly in light of individual susceptibility,” the authors wrote.

Reference

Li J, Yang L, Yao Y, et al. Associations between long-term night shift work and incidence of chronic obstructive pulmonary disease: a prospective cohort study of 277,059 UK Biobank participants. BMC Med. 2024;22(1):16. doi:10.1186/s12916-023-03240-8