Altered Sleep patterns by night shift and smoking associated with Lung cancer risk in women
France: Researchers from France found that altered sleep patterns due to the long duration of night shift work and tobacco smoking are associated with lung cancer in women. The study results were published in the International Journal of Environmental Research and Public Health.
Circadian rhythm is a natural internal process that regulates the sleep-wake cycle. Any disturbance in the rhythm due to night shift work and/or sleep disorders is associated with negative health outcomes including cancer. But unlike breast and prostate cancer there is limited data on the association of lung cancer with circadian rhythm. Hence Emilie Cordina-Duverger et al from France conducted a population-based case-control study called the WELCA study to explore the role of sleep disorders and night shift work in lung cancer risk among women from 2014-2017.
The WELCA study was carried out among women living in France's Île-de-France region. Participants who had given in-person interviews conducted by trained research nurses were enrolled in the study. There were 716 patients with lung cancer (n=716) and 758 control participants without lung cancer. The participant's relationships to sleep traits, night shift work, smoking status, and sleep disorder index (SDI) were noted.
The following were considered:
| Sleep traits |
|
| Sleep Duration |
|
| short sleep duration | <7 hours/day |
| normal sleep duration | 7-7.9 hours/day |
| long sleep duration | ≥8 hours/day |
| sleep chronotype | the natural inclination to sleep more in the morning or evening as compared with the neutral type, which is the normal referent |
| Night shift work, | the duration and the maximum frequency of night shift work. |
| Tobacco exposure |
|
The odds ratios (OR) and 95% confidence intervals (CI) associated with sleep duration per day, a summary index of sleep disorders, chronotype, and night shift work exposure metrics were measured using multivariable logistic regression models.
Findings:
• The OR was 1.39 (95% CI 1.04-1.86) in long sleepers (≥8 h) and 1.16 (95% CI 0.86-1.56) in short sleepers (<7 h) when compared to women with an average sleep duration of 7-7.9 h per day.
• Regardless of the duration of night work or the frequency of night shifts, lung cancer was not associated with the sleep disorder index, nor with night shift work.
• But an elevated OR associated with the sleep disorder index was found in the subgroup of current smokers.
• In women who worked at night for ≥5 years, a U-shaped association of lung cancer with sleep duration was more pronounced.
Thus, The WELCA study concluded that adverse risk of lung cancer was associated with long-term night workers and smokers among women, and also short sleepers (<7 h/day) and long-sleepers (≥8 h per day) were at an increased risk of lung cancer as compared to normal sleepers.
Further reading: Cordina-Duverger E, Uchai S, Tvardik N, et al. Sleep Traits, Night Shift Work and Lung Cancer Risk among Women: Results from a Population-Based Case-Control Study in France (The WELCA Study). Int J Environ Res Public Health. 2022;19(23):16246. Published 2022 Dec 4. doi: 10.3390/ijerph192316246
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