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. / published_or_final_version / Community Medicine / Master / Master of Public Health

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Submitted in fulfilment of the requirements for the Degree of Masters in Technology: Environmental Health, Durban University of Technology, 2017. / Shift work is a necessity for many organizations. Reasons for shift work are mainly to ensure continuous and optimized operations. Many studies on shift workers have concluded that it can lead to adverse physiological, social and psychological health effects. This study examines challenges associated with working shifts at a biscuits manufacturing factory. Results should be able to assist the employer in implementing effective interventions directed at limiting the negative effects of shift work on employees. This is a convergent parallel design multi method stud among 152 shift workers in a biscuits manufacturer located in Durban, KwaZulu Natal. An abbreviated and modified form of the validated SSI questionnaire was used (Barton et al. 1995). The questionnaire contained a battery of items designed to examine the relationship of health and personal adjustment to shift work. Owing to the exploratory nature of the study, a focus group methodology was also used and this allowed for in-depth qualitative research which catered for a more comprehensive understanding of the current shift work issues. A retrospective review of injury records of employees who sustained occupational injuries between 2012 and 2013 was also conducted. The sample comprised of 85 (56%) males and 63 (42%) females. Logistic regression was used to estimate the association between shift work and the likelihood of sleep disturbance, poor health outcomes and limited time for social and domestic activities, adjusting for age, sex, partner working, years working night shift, marital status, job class and years employed. Odds ratio (OR) for reported sleep disturbance was slightly higher among women (OR=1.65; 95% CI = 0.25; 10.84; p < 0.05) compared to males, but this was not statistically significant. Longer shift work experience (i.e.11-20 years) was significantly associated with better health status (OR=0.18; 95%CI = 0.06; 0.46; p < 0.05). Shift work experience (11 to 20 years) was also found to be significantly associated with limited time for both social (OR = 0.10; 95%CI = 0.03; 0.30) and domestic activities (OR= 0.25; 95% CI = 0.11; 0.57; p < 0.05) (Table 4). Age had no effect on social and domestic activities, but those 40 years and above were more likely to have limited time for social and domestic activities (OR = 3.06; 95%CI =0.60; 15.60 and OR= 2.5; 95%CI=0.47; 13.06). Those with more shift work experience seemed to have more time for social and domestic activities compared to those with less than 10 years experience. Findings from the FGD’s revealed that most participants (91%) did not get sufficient sleep time after night shift; this was mainly because of the chores they had to do after getting home form night shift and disturbances from the household and neighbours. The average time spent sleeping by majority of participants after night shift was 5 hours. Swollen feet, gastric, sleep disorders, indigestion and headaches were some common complaints experienced by shift workers in this study. About 27% of participants reported to have been injured at work before. These incidents were reported to be related to drowsiness and fatigue. The company’s incident records showed a total of 160 injuires between 2012 and 2013, of which 38 occurred during night shift. In 2012, the company recorded 65 injuries which included 51 first aid (FA) injuries, 6 minor injuries (MI) and 8 lost time (LT) injuries, as categorized by the company. 2013 had the highest number of incidents, with 95 total injuries, averaging to 7.9 injuries annually. There were 84 first aid incidents recorded for year 2013, 9 minor injuries and only 2 lost time injuries. Twenty three percent (15, n=65) incidents occurred during night shift in year 2012, of which 11% (7, n=65) were females. The number of night shift incidents slightly increased to 24% (23, n=95) in 2013 and females accounted for 9.40%. The records showed that majority of injuries happened between 17h00 and 21h00 at night. Results of this study provides evidence that shift work impacts negatively on the lives of the employees and can lead to adverse health outcomes such as poor dietary intake, headaches and swollen feet to mention but a few. / M

Breast cancer poses a serious public health concern. This case-control study describes the relationship of night-shift working on the development of breast cancer in 57 women diagnosed with breast cancer compared to 49 women with other types of cancer in the Vaal Triangle area (selected through non-probability purposive sampling from CANSA). The study revealed that women who work night-shift developed breast cancer 1.24 times more often than women who do not work nightshift (OR=1.24 [95% CI 0.52 to 2.89]). The odds ratio was further increased in women who worked rotating-shift (OR=1.44 [95% CI 0.58 to 3.59]). Night-shift work exposure was not statistically related to the development of breast cancer. It is recommended that the relationship between night-shift exposure and breast cancer risk be further explored through cross-sectional and cohort studies, and other breast cancer pathways. / Health Studies / M.A. (Public Health)

Breast cancer poses a serious public health concern. This case-control study describes the relationship of night-shift working on the development of breast cancer in 57 women diagnosed with breast cancer compared to 49 women with other types of cancer in the Vaal Triangle area (selected through non-probability purposive sampling from CANSA). The study revealed that women who work night-shift developed breast cancer 1.24 times more often than women who do not work nightshift (OR=1.24 [95% CI 0.52 to 2.89]). The odds ratio was further increased in women who worked rotating-shift (OR=1.44 [95% CI 0.58 to 3.59]). Night-shift work exposure was not statistically related to the development of breast cancer. It is recommended that the relationship between night-shift exposure and breast cancer risk be further explored through cross-sectional and cohort studies, and other breast cancer pathways. / Health Studies / M. A. (Public Health)

Text in Afrikaans / Summaries in English and Afrikaans / This study aims to investigate the relation between a crane operator in a slab handlingarea's experience of his/her work environment and occupational health. A study of the literature leads one to the conclusion that the nature of crane operators' work environment may cause health problems. According to the literature crane operators are high risk cases regarding musculoskeletal disorders. The empirical study affirms that there are risk factors present in the crane operator's work environment, which may influence his/her occupational health. It is statistically proven that there is a meaningful difference between crane operators with a negative experience of the work environment and crane operators with a positive experience of the work environment, and the amount of illnesses experienced by crane operators as well as their general health. Recommendations are made regarding training, adjustability and flexibility of the work station, job rotation, job expansion and enrichment, and social contact. / Die doel van die studie is om die verband tussen 'n kraanoperateur in 'n platblokhanteringsarea se ervaring van sy/haar werksomgewing en beroepsgesondheid te ondersoek. Die literatuurstudie lei tot die gevolgtrekking dat die aard van kraanoperateurs se werksomgewing aanleiding kan gee tot gesondheidsprobleme. Volgens die literatuur is kraanoperateurs hoerisikogevalle ten opsigte van spierskeletstelselbeserings. Die empiriese studie bevestig dat daar risikofaktore voorkom in die kraanoperateur se werksomgewing wat sy/haar beroepsgesondheid kan be"invloed. Statisties is bewys dat daar 'n betekenisvolle verskil is tussen kraanoperateurs met 'n negatiewe ervaring van die werksomgewing en kraanoperateurs met 'n positiewe ervaring van die werksomgewing en die hoeveelheid siektetoestande wat kraanoperateurs ervaar, en die algemene gesondheid van kraanoperateurs. Aanbevelings om risikofaktore te beheer word gemaak ten opsigte van opleiding, verstelbaarheid en buigbaarheid van die werkstasie, posrotasie, posverbreding en - verryking, en sosiale kontak. / Industrial Psychology / M. Com (Industrial Psychology)

Text in Afrikaans / Summaries in English and Afrikaans / This study aims to investigate the relation between a crane operator in a slab handlingarea's experience of his/her work environment and occupational health. A study of the literature leads one to the conclusion that the nature of crane operators' work environment may cause health problems. According to the literature crane operators are high risk cases regarding musculoskeletal disorders. The empirical study affirms that there are risk factors present in the crane operator's work environment, which may influence his/her occupational health. It is statistically proven that there is a meaningful difference between crane operators with a negative experience of the work environment and crane operators with a positive experience of the work environment, and the amount of illnesses experienced by crane operators as well as their general health. Recommendations are made regarding training, adjustability and flexibility of the work station, job rotation, job expansion and enrichment, and social contact. / Die doel van die studie is om die verband tussen 'n kraanoperateur in 'n platblokhanteringsarea se ervaring van sy/haar werksomgewing en beroepsgesondheid te ondersoek. Die literatuurstudie lei tot die gevolgtrekking dat die aard van kraanoperateurs se werksomgewing aanleiding kan gee tot gesondheidsprobleme. Volgens die literatuur is kraanoperateurs hoerisikogevalle ten opsigte van spierskeletstelselbeserings. Die empiriese studie bevestig dat daar risikofaktore voorkom in die kraanoperateur se werksomgewing wat sy/haar beroepsgesondheid kan be"invloed. Statisties is bewys dat daar 'n betekenisvolle verskil is tussen kraanoperateurs met 'n negatiewe ervaring van die werksomgewing en kraanoperateurs met 'n positiewe ervaring van die werksomgewing en die hoeveelheid siektetoestande wat kraanoperateurs ervaar, en die algemene gesondheid van kraanoperateurs. Aanbevelings om risikofaktore te beheer word gemaak ten opsigte van opleiding, verstelbaarheid en buigbaarheid van die werkstasie, posrotasie, posverbreding en - verryking, en sosiale kontak. / Industrial Psychology / M. Com (Industrial Psychology)