An overview of trends in night work in France over 34 years, by occupation and industry, using census data and a "gendered" job-exposure matrix
A 34-year overview of night work by occupation and industry in France based on census data and a gender-specific job-exposure matrix.
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Night work takes many forms, involving work schedules outside normal hours, often alternating between day and night shifts. In Europe and the United States, night work has increased in recent decades and affects 19 to 25% of all workers. In France, women’s access to night work was, until 2001, limited to certain sectors. Since then, it has no longer been subject to such restrictions in accordance with European law based on the principle of professional equality between men and women.
Several occupations across various sectors or services involve tasks that must be performed 24 hours a day, 7 days a week. The main sectors with such constraints are health and safety, but also certain industrial activities requiring continuous production.
The impact of night work on health is well documented. Some of these effects are due to disruptions in the circadian rhythm (the biological clock regulating the day-night cycle), which can affect well-being and health. Effects on alcohol consumption, diet, sleep, reproduction, mental health, diabetes, certain cancers, etc., have been described for specific professions. Due to its unique nature, night work requires enhanced individual medical monitoring. In 2019, shift work involving night shifts was classified as “probably carcinogenic” to humans (Group 2A) by the International Agency for Research on Cancer (IARC).
Drawing on census data and job-exposure matrices, this article published in the journal BMC – Public Health [1] provides, for the first time, an estimate of the number and proportion of night workers in France, by occupation and economic sector. It analyzes trends over a 34-year period from 1982 to 2015.
3 questions Marie-Tülin Houot, Data Support, Processing, and Analysis Division, Santé publique France, and Corinne Pilorget, Health, Environment, and Work Division, Santé publique France
In occupational risk epidemiology, it is important to be able to account for risk factors associated with exposure to a variety of workplace hazards of different types (chemical, biological, or physical hazards; postural or organizational stressors; psychosocial risks). Job-exposure matrices make it possible to assess exposure to these various risk factors based solely on knowledge of jobs (occupation within a sector of activity), thereby avoiding the need to ask workers about the specific hazards of their jobs, of which they are not always aware.
Regarding night work, information on this topic for each worker is not always collected in studies, or is collected only for a specific period and may not be known for the entire professional career. The job-exposure matrix for night work provides, by occupation and for five-year periods between 1993 and 2012, the probability of having worked between midnight and 5 a.m., either regularly or occasionally. The analysis was differentiated by gender due to night work regulations that significantly restricted night work for women prior to 2001. Two “gendered” job-exposure matrices are therefore available to specifically document night work among men on the one hand, and among women on the other.
This matrix was constructed retrospectively using data from INSEE’s annual employment surveys. In these surveys, which covered approximately 150,000 people, the same question regarding night work performed in the primary job was asked between 1993 and 2012. These individual data were combined by 5-year periods, and the proportion of regular and occasional night workers among men and women was estimated for each occupation and each period. The occupation-exposure matrices are available on the Exp-Pro portal.
Night work, considered as a whole—including both regular and occasional night work—increased only slightly in proportion between 1982 and 2015 (15.8% vs. 16.4%), representing 3,670,000 night workers in 1982 and 4,370,000 in 2015 in France.
The first notable trend in the evolution of night work over the 34-year period studied concerns the shift in the ratio between occasional and regular night work. In 1982, regular night work accounted for 24% of total night work, whereas by 2015 its share had nearly doubled, reaching 42%.
The second key finding concerns the difference in night work between men and women. The trend in night work over the period studied is minimal among men, with approximately 22% working at night, whereas it is marked among women, who increased from 7% to 10% over the same period. The difference is all the more significant when night work is regular. Thus, among women, the proportion of regular night work increased sharply between 1982 and 2015 (+150%), due to regulatory changes, rising from 173,000 regular female night workers in 1982 to 581,000 in 2015. Notably, there was a 69% increase between 1999 and 2007 in the proportion of women who regularly work night shifts, whereas, over the same period, the proportion of women in the workforce increased by only 4.5%. Among men, the number of workers who regularly work night shifts rose from 712,000 to 1.20 million over the period (+74% in proportion).
The sectors showing a marked increase in night work are linked to service activities (1.97 million night workers in 1982 to 3.3 million in 2015), notably including the transportation and health sectors.
The study presented in this article was conducted in collaboration with the Inserm “Exposome and Heredity” team at the Center for Research in Epidemiology and Population Health (1), which will use the night work matrices to assess this exposure in their studies on breast cancer in both women and men. These matrices may also be made available to other research teams, like the other job-exposure matrices from Santé publique France’s Matgéné program (see box: Matgéné Program – Job-Exposure Matrices).
Since 2019, the IARC has classified shift work involving night shifts as a probable human carcinogen (Group 2A). Cross-referencing the night work matrices with population data from a sample of occupational histories collected in parallel with Santé publique France’s 2020 and 2021 Health Barometers will enable the production of exposure indicators covering the entire professional career. These estimates of the proportion of exposed workers—taking into account all jobs held by workers throughout their careers—will then be used to calculate the contribution of night work exposure to the occurrence of several diseases, including breast cancer, that is, the fraction of risk attributable to this occupational exposure. These data will supplement the information already available regarding the burden of disease.
Matgéné Program - Job-Exposure Matrices
The development of tools to assess occupational exposures is necessary to improve understanding and monitoring of occupational risks. Santé publique France coordinates the Matgéné program, which aims to develop occupation-exposure matrices tailored to the general French population to generate occupational exposure indicators. An occupation-exposure matrix can be briefly described as a table showing the correspondence between occupations (professions practiced in a sector of activity) and exposure indices (probability, level) to one or more hazards. When these matrices are cross-referenced with individual occupational data, exposures are automatically assigned to individuals based on the jobs they hold. These matrices have numerous potential applications in the field of occupational health surveillance and research.
They can be used:
to estimate the proportion and prevalence of occupationally exposed individuals in the general population and describe the occupations and sectors most affected at a given point in time or over the course of a professional career;
to contribute to the estimation of the proportion of risk attributable to occupational exposure (disease burden);
to assess occupational exposures among study participants in epidemiological studies;
to assist in identifying exposures for the prevention or medical and social care of workers.
The job-exposure matrices of the Matgéné program are specifically tailored to the working population in France. They provide an assessment for past and current exposure periods, thereby enabling the documentation of past exposures whose impact on current diseases is proven or suspected. Finally, they document exposure for all workers, whether they are employees or self-employed, and whether they work in the public or private sector.
The Matgéné matrices currently available or under development cover exposure to mineral dusts (silica, cement), organic dusts (leather, flour, grains, wood), solvents (petroleum-based solvents and fuels, chlorinated solvents, oxygenated solvents), fibers (asbestos, mineral wool, refractory ceramic fibers), formaldehyde, pesticides, noise, and night work.
The matrices are available on the Exp-Pro portal, and occupational exposure indicators are available on the Géodes portal.
The matrices and indicators are available upon submission of a reasoned request to dset-matgene@santepubliquefrance.fr
Learn more: https://exppro.santepubliquefrance.fr/matgene
[1] Houot, M.T., Tvardik, N., Cordina-Duverger, E., et al. A 34-year overview of night work by occupation and industry in France based on census data and a sex-specific job-exposure matrix. BMC Public Health, 22, 1441 (2022).
(1) Emilie Cordina-Duverger, Pascal Guénel, Nastassia Tvardik.
Learn more:
Occupational exposures and the Job-Exposure Matrices:
Fels A, Houot M, Garras L, Delabre L, Pilorget C. Employed and self-employed workers in France between 2007 and 2015: description of populations and identification of differences in occupational exposure. Weekly Epidemiological Bulletin, 2021; (2): 22-31.
Garras L, Delabre L, Houot M, Pilorget C. Overview of occupations and sectors exposed to formaldehyde in 2017. Occupational Health and Safety, 2021; (264): 70-83.
Lagarrigue R, Houot M, El Yamani M, Pilorget C, Groupe M. Occupational exposure to oxygenated, petroleum-based, and chlorinated solvents among women of childbearing age in France in 2013. Results of the Matgéné program. Weekly Epidemiological Bulletin, 2019; (7): 137-43.
Pilorget C, Lagarrigue R, Houot M, Matgéné G. Trends in occupational exposure to oxygenated, petroleum-based, and chlorinated solvents in France between 1999 and 2013. Results of the Matgéné program. Weekly Epidemiological Bulletin, 2018; (12-13): 234-40.
El Yamani M, Fréry N, Pilorget C. Assessment of occupational exposures among the working population in France: tools and methods. Weekly Epidemiological Bulletin, 2018; (12-13): 216-20.
Occupation-exposure matrices and the burden of disease:
Gilg Soit Ilg A, Houot M, Pilorget C. Estimation of the proportion of cancers attributable to certain occupational exposures in France. Use of job-exposure matrices developed as part of the Matgéné program. Saint-Maurice: Santé publique France, 2016: 40 p.
Marant Micallef C, Charvat H, Houot MT, Vignat J, Straif K, Paul A, et al. Estimated number of cancers attributable to occupational exposures in France in 2017: an update using a new method for improved estimates. J Expo Sci Environ Epidemiol., 2021. Jun 25.
Indicators of night work exposure in France available for free access at:
Prevalence rate of occupational exposure to night work in the working-age population.
Prevalence rate of occupational exposure to occasional night work in the employed working-age population.
Prevalence rate of occupational exposure to regular night work in the employed working-age population.
