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postgraduate thesis: Night shift work and risk of breast cancer in women: a literature review

TitleNight shift work and risk of breast cancer in women: a literature review
Authors
Issue Date2011
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Abstract
Background Night shift work is inevitable for maintaining continuous services in different sectors e.g. healthcare, financial, transport and service sectors. Night shift work increases exposure of light at night. Exposure of light at night suppresses production of a neurohormone melatonin. Melatonin has shown potential cancer protective action in animal experiments. Melatonin deficiency is suggested to be related to the development of various cancer especially breast cancer. Breast cancer incidence in Hong Kong is rising. Particular concern about association between night shift work and breast cancer is raised. Objective To collect evidence from studies of other countries with study populations of different professions and to evaluate the relationship between night shift work and breast cancer Method MEDLINE was searched to identify publications, limited to English articles, from 1973 to May 2011. Search terms include (circadian rhythm or night work or night shift or shift work or work schedule tolerance) and (cancer or neoplasm or neoplasia) and (risk or rate or incidence). No restriction was set to the publication type. Results Altogether 343 titles retrieved from MEDLINE search. Finally, 8 primary observational studies that met inclusion criteria were identified for this review. Of these, two were prospective cohort studies, one was retrospective cohort study, two were nested case-control studies and three were case-control studies. Most of the study had crude exposure assessment of night shift work, in which four studies relied on group level of exposure probability instead of individual exposure information. Six of eight studies showed positive results on the association of night shift work and breast cancer in women. Three studies found that risk of breast cancer was increased significantly for those who had engaged in night shift work in a long duration i.e. more than 20-30 years, but they were all conducted in populations of same occupational group i.e. nurse and only a moderate increase of breast cancer risk was found. The results were subject to confounding and bias. No consistent results were found for effect of shorter duration of night shift work on risk of breast cancer. Conclusion Based on the studies included, there is suggestive evidence of an association of night shift work and breast cancer. Further studies on this are needed. Involvement of population of different occupational groups, controlling confounder of hormone use and conducting exposure assessment with high reliability using individual information instead of that from group are suggested.
DegreeMaster of Public Health
SubjectShift systems - Health aspects.
Breast - Cancer - Risk factors.
Dept/ProgramCommunity Medicine

 

DC FieldValueLanguage
dc.contributor.authorCheng, Shuk-wai, Sherry.-
dc.contributor.author鄭淑慧-
dc.date.issued2011-
dc.description.abstractBackground Night shift work is inevitable for maintaining continuous services in different sectors e.g. healthcare, financial, transport and service sectors. Night shift work increases exposure of light at night. Exposure of light at night suppresses production of a neurohormone melatonin. Melatonin has shown potential cancer protective action in animal experiments. Melatonin deficiency is suggested to be related to the development of various cancer especially breast cancer. Breast cancer incidence in Hong Kong is rising. Particular concern about association between night shift work and breast cancer is raised. Objective To collect evidence from studies of other countries with study populations of different professions and to evaluate the relationship between night shift work and breast cancer Method MEDLINE was searched to identify publications, limited to English articles, from 1973 to May 2011. Search terms include (circadian rhythm or night work or night shift or shift work or work schedule tolerance) and (cancer or neoplasm or neoplasia) and (risk or rate or incidence). No restriction was set to the publication type. Results Altogether 343 titles retrieved from MEDLINE search. Finally, 8 primary observational studies that met inclusion criteria were identified for this review. Of these, two were prospective cohort studies, one was retrospective cohort study, two were nested case-control studies and three were case-control studies. Most of the study had crude exposure assessment of night shift work, in which four studies relied on group level of exposure probability instead of individual exposure information. Six of eight studies showed positive results on the association of night shift work and breast cancer in women. Three studies found that risk of breast cancer was increased significantly for those who had engaged in night shift work in a long duration i.e. more than 20-30 years, but they were all conducted in populations of same occupational group i.e. nurse and only a moderate increase of breast cancer risk was found. The results were subject to confounding and bias. No consistent results were found for effect of shorter duration of night shift work on risk of breast cancer. Conclusion Based on the studies included, there is suggestive evidence of an association of night shift work and breast cancer. Further studies on this are needed. Involvement of population of different occupational groups, controlling confounder of hormone use and conducting exposure assessment with high reliability using individual information instead of that from group are suggested.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.source.urihttp://hub.hku.hk/bib/B47560046-
dc.subject.lcshShift systems - Health aspects.-
dc.subject.lcshBreast - Cancer - Risk factors.-
dc.titleNight shift work and risk of breast cancer in women: a literature review-
dc.typePG_Thesis-
dc.identifier.hkulb4756004-
dc.description.thesisnameMaster of Public Health-
dc.description.thesislevelmaster's-
dc.description.thesisdisciplineCommunity Medicine-
dc.description.naturepublished_or_final_version-
dc.date.hkucongregation2012-

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