Night work, sleep disruption and long-COVID risk: a population-based cohort study, 2026, Papantoniou et al.

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Night work, sleep disruption and long-COVID risk: a population-based cohort study

Papantoniou, Kyriaki; Espinosa, Ana; Karachaliou, Marianna; Lassale, Camille; Castaño-Vinyals, Gemma; Harding, Barbara N; De Matteis, Sara; Straif, Kurt; Alonso-Nogués, Eva; Dobaño, Carlota; Moncunill, Gemma; Blay, Natalia; Iraola-Guzmán, Susana; de Cid, Rafael; Garcia-Aymerich, Judith; Kogevinas, Manolis

Abstract​

Objective Circadian and sleep disruption may increase the risk and severity of SARS-CoV-2 infections, but the role of night shift work and disturbed sleep in the development of long-COVID remains inadequately investigated.
We prospectively examined the association of night work and sleep disturbances with risk of long-COVID.

Methods We followed participants of the COVICAT study, a population-based cohort of adults in Catalonia, Spain between 2021 and 2023.
Night shift work and sleep characteristics were assessed in 2021.
Long-COVID was defined as the report of persistent symptoms (>3 months) after a SARS-CoV-2 infection.
Poisson regression analysis was performed to evaluate the independent and joint effects of night shift work and sleep disturbances including chronic insomnia with risk of long-COVID.
Analyses were stratified by sex, body mass index and chronotype.

Results During the two-year follow-up, 284 of the 1899 newly infected participants reported long-COVID symptoms.
Compared to day workers, night shift workers had 88% higher risk of developing long-COVID [95% confidence interval (CI) 1.29–2.72], after adjusting for potential confounders.
The risk further increased among night workers with obesity.
Chronic insomnia in the general population was associated with 42% increased risk of long-COVID (95% CI 1.12–1.78). Night workers with chronic insomnia had a 2.7 fold higher long-COVID risk (95% CI 1.60–4.51) compared to day workers without chronic insomnia.
Associations persisted in various sensitivity analyses.

Conclusions Our findings from a large prospective cohort indicate that night shift work and poor sleep are independently and jointly associated with a higher risk of long-COVID.

PDF | Web | DOI | Scandinavian Journal of Work, Environment & Health | Open Access
 
https://www.eurekalert.org/news-releases/1139037

NEWS RELEASE 6-AUG-2026

Night shift work linked to a higher risk of long COVID​

People working night shifts were nearly twice as likely to develop long COVID, while chronic insomnia further increased the risk, according to a study based on the COVICAT cohort

Peer-Reviewed Publication
BARCELONA INSTITUTE FOR GLOBAL HEALTH (ISGLOBAL)


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The first evidence that night work and chronic insomnia may increase the risk of developing long COVID comes from a new study led by ISGlobal, a centre supported by “la Caixa” Foundation, in collaboration with the Germans Trias i Pujol Research Institute (IGTP), through the GCAT | Genomes for Life cohort. The findings, published in the Scandinavian Journal of Work, Environment and Health, highlight the importance of healthy sleep habits in preventing long COVID and other post-acute infectious syndromes.

Studies in humans show that disrupting the body's internal clock can weaken immune responses and increase susceptibility to infections. During the COVID-19 pandemic, a study in UK found that sleep disturbances were linked to a higher risk of SARS-CoV-2 infection. “However, no previous study had evaluated whether disrupting the body’s biological clock also increases the risk of developing long COVID”, says first author Kyriaki Papantoniou, Associate Professor at the Medical University of Vienna and Associated Researcher at ISGlobal.

Night shift workers at increased risk of long COVID

In this study, the research team followed 2,941 adults in the population-based COVICAT cohort in Catalonia between 2021 and 2023. Among the 1,899 participants who became infected with SARS-CoV-2, 284 developed long COVID - defined as having persistent symptoms lasting for more than three months after the infection - during the 2-year follow-up.

Compared with day workers, those working night shifts had an 88% higher risk (i.e. almost double) of developing long COVID after accounting for other risk factors such as vaccination history or chronic diseases. This association was stronger in night workers with obesity. Moreover, the increased risk was observed both in current and former night workers, suggesting that it reflects longer-term effects of circadian disruption rather than short-term changes.

In contrast, night shift work was not associated with a higher risk of becoming infected, suggesting that disruption of the biological clock may influence how the body recovers from infection rather than the likelihood of catching the virus.

"Our findings suggest that circadian disruption plays a role in the transition from acute infection to persistent symptoms," says ISGlobal researcher Manolis Kogevinas, who coordinated the study.

Poor sleep further amplifies the risk

The researchers found that chronic insomnia also increased the risk of long COVID by 42%, independently of night shift work. Together, the two factors had a synergistic effect: night shift workers with chronic insomnia were 2.7 times more likely to develop long COVID than day workers without insomnia.

The biological mechanisms involved are not yet fully understood, but the time of day when the body encounters a pathogen may influence the immune response. In addition, disruption of the body's biological clock can impair the immune system’s ability to clear the infection.

Improving sleep as a preventive strategy

Given the increase of insomnia prevalence in the general population, the authors underline the need to understand the short and long-term effects of disturbed sleep on infection-related outcomes. In any case, the findings point to sleep as a potentially modifiable factor in preventing long COVID and other post-infectious conditions.

"Promoting healthy sleep habits and minimising circadian disruption could represent simple, low-cost strategies to reduce the long-term consequences of viral infections, particularly among people who work night shifts," concludes Kogevinas.

The researchers note that the study's strengths include the use of a well-characterised population-based cohort with detailed information on work schedules, sleep habits and health, as well as an internationally recognised definition of long COVID. However, the participants were aged 40 to 65 years, so the findings may not necessarily apply to younger or older populations, and other occupational factors, such as work-related stress, cannot be completely ruled out.



Reference

K. Papantoniou, A. Espinosa, M Karachaliou, C Lassale, G Castaño-Vinyals, B Harding, De Matteis S, Straif K, E Alonso, C Dobaño, G Moncunill, N Blay, S Iraola-Guzmán, R de Cid, J Garcia-Aymerich, M Kogevinas. Night work, sleep disruption and long-COVID risk: a population-based cohort study. SJWEH. 2026. Doi: 10.5271/sjweh.4318

DOI​

10.5271/sjweh.4318

METHOD OF RESEARCH​

Meta-analysis

SUBJECT OF RESEARCH​

People

ARTICLE TITLE​

Night work, sleep disruption and long-COVID risk: a population-based cohort study

ARTICLE PUBLICATION DATE​

4-Aug-2026

COI STATEMENT​

The authors declare no competing interests.
 
Asymptomatic acute infections —

During the 2-year follow-up period, among 2941 participants at risk for SARS-CoV-2 infection, 1899 were newly infected with SARS-CoV-2, of whom 283 developed long-COVID (280 cases ascertained through questionnaire, 3 cases identified through EHR). The vast majority of the infections during this period were mild or moderate (N=1562; 82%), 330 (17.3%) were asymptomatic and only 7 (0.4%) were severe or critical infections.
Click to expand...
 
SNT Gatchaman said:
Asymptomatic acute infections —
Click to expand...
From this paper:
We classified the severity of SARS-CoV-2 infection according to WHO, based on self-reported information, as asymptomatic (no symptoms reported), mild/moderate (≥1 symptom), severe (hospitalization), and critical
Click to expand...

From
Universal SARS-CoV-2 RT-qPCR admission screening over 21 months in a German tertiary care hospital: detection of asymptomatic infections, 2026, Eiter+
Out of 111,271 screened individuals, 705 (0.6%) tested positive for SARS-CoV-2 by RT-qPCR.
Among these, 236 cases (0.2%) had not been previously diagnosed and were identified through RT-qPCR admission screening.
Of the newly detected cases,110 (0.1%) were asymptomatic without any known positive contact history.
Click to expand...
 
In that other paper they present that asymptomatic data a bit more clearly in the results —

Of the 236 individuals initially identified as SARS-CoV2-positive through the RT-qPCR admission screening, 92/236 (39.0%) exhibited typical COVID-19 symptoms, whereas 144/236 (61.0%) were asymptomatic at the time of testing. Among the asymptomatic individuals, 18/144 (12.5%) were presymptomatic and developed symptoms after screening.
Click to expand...

144/236 (61%) were asymptomatic initially but 18 of those went on to become symptomatic after testing. So 126/236 (53%) remained asymptomatic.
 
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