| Shift work is an employment practice designed to make workers taking turns to have a rest and factories or service unit (like hospital, police station and transportation industry) running all day. Accumulating evidences showed that, the population of various kind of shift work took up more than 20 percent of the whole population in many industry countries, and it is still growing. Shift work might cause some corresponding physical damage for shift workers. Therefore, shift work and its related health damage for shift workers deserved more attention.Therefore, we hoped to get a better understanding of the association of shift work duration, duration of leaving shift work and types of shift work with sleeping quality, MetS and DM in this study.The main contents are as follows:Part One Relationship between Shift Work and Sleeping Quality in Retired WorkersObjective:To investigate the association between shift work duration and sleeping quality; as well as discussing the influence of leaving shift work duration on the relationship of shift work duration and sleeping quality; To investigate the relationship between different types of shift work and sleeping quality in retired workers.Methods:Sleeping quality in the last year was evaluated by three pre-specified response categories:normal quality, impaired quality, and poor quality. The questions were simplified according to Pittsburgh Sleep Quality Index (PSQI) at 2008. In 2013, sleeping quality was investigated using full version of PSQI. Kappa value was calculated to test the consistency of self-reported sleeping quality in 2008 and Pittsburgh Sleep Quality Index in 2013. The differences between shift workers and day workers on demographic characteristics and clinical indexes were compared using Student-t test for continuous variables and Chi-square test for categorical data. For further analysis, univariate and multivariate logistic regression were used.Results:For relationship between shift work duration and sleeping quality, we included 26,463 participants in this study, among which 9,118 (34.46%) were shift workers. In the categorical analysis, compared with day workers, the adjusted odds ratio (ORs) (95% confidence interval [CI]) were 1.33(1.06-1.66),1.12(1.03-1.23),1.06(1.02-1.10), and 1.07(1.00-1.14) for 1-4 years,5-9 years,10-19 years, and>20 years shift work, respectively. There was no such association observed between shift work and impaired sleeping quality. In the continuous analysis, the ORs (95%CI) was 1.11(1.03-1.21) for 20 years increment of shift work. When leaving shift work for 20 years or above, the relationship between shift work duration and poor sleeping quality tended to become obscure. Additionally, stratified analysis according to sex, age, BMI and smoking status indicated that the association between shift work duration and sleeping quality could not be modified by these stratified factors.For relationship between types of shift work and sleeping quality, we included 9,559 retired workers. We compared the two investigating methods of sleeping quality by calculating Kappa value, the Kappa value and 95%CI was 0.76 (0.75-0.77) for these two methods. Compared with day workers, the adjusted ORs (95%CI) for poor sleeping quality were 1.19 (0.99-1.44),1.31(1.05-1.65) and 2.16(0.84-5.58) for two shifts, three shifts and four shifts, respectively, and P trend value was 0.002. All the shift work types in this study had no significant association with impaired sleeping quality. Moreover, the relationship between shift work types and sleeping quality could not be modified by sex, age, BMI and smoking status in stratified analysis.Conclusion:shift work was significantly related with sleeping quality decline, and the strength of their relationship weakened with the extension of shift work duration. When leaving shift work for 20 years or above, the relationship between shift work and sleeping quality was insignificant. Two shifts was the most common type of shift work. Compared with day workers, four shifts had the strongest relationship with poor sleeping quality while two shifts did not significantly related with poor sleeping quality.Part Two Relationship between Shift Work and Metabolic Syndrome in Retired WorkersObjective:To investigate the association between shift work duration and MetS; as well as discussing the influence of leaving shift work duration on the relationship of shift work duration and MetS; to investigate the relationship between different types of shift work and metabolic syndrome in retired workers.Methods:MetS is defined as a cluster of several metabolic factors. In this study, we defined MetS according to the diagnostic criteria proposed by the Adult Treatment Program III of the National Cholesterol Education Program (NCEP ATP III,2005). The differences between shift workers and day workers on demographic characteristics and clinical indexes were compared using Student-t test for continuous variables and Chi-square test for categorical data. To compare the relationship between shift work duration and types of shift work groups and MetS, logistic regression was used.Results:For relationship between shift work duration and MetS, we included 26,382 retired workers, in which 9,088 participants were shift workers (34.45%). Shift work was significantly related with the prevalence of MetS, and the association increased as the shift work duration extended. After adjustment,the ORs (95% Cl) for MetS was 1.16(1.01-1.31) for people worked for 20 years or above in a shift position. Further analysis according to sex found that the relationship between shift work and MetS had significant gender difference. After leaving shift work position for 20 years or above, shift work was no longer related with the prevalence of MetS.For relationship between types of shift work and MetS, we finally included 8,940 participants in the analysis. In all models, two shifts and three shifts were not significantly related with MetS. Stratified analysis showed that only sex could modified the relationship between types of shift work and MetS, three shifts increased the prevalence of MetS in female workers, the OR (95%CI) was 1.37(1.01-1.88).Conclusion:Shift work was related with MetS, the prevalence of MetS was markedly increased in people worked for 20 years or above in a shift position. There was a gender difference in the relationship between shift work and MetS. The association weakened with the extension of leaving shift work duration. And compared with day workers, two shifts and three shifts were not significantly related with MetS, except that three shifts increased prevalence of MetS in female workers.Part Three Relationship between Shift Work and Diabetes in Retired WorkersObjective:To investigate the association between shift work duration and DM; as well as discussing the influence of leaving shift work duration on the relationship of shift work duration and DM. and to investigate the relationship between different types of shift work and DM in retired workers.Methods:In this study, diabetes was diagnosed if participants met any of the following standards:(1) fasting plasma glucose level> 7.0 mmol/1; repeated measurements were done to confirm the diagnosis on different days if the participants do not have any symptoms of diabetes. (2) self-reported clinically diagnosed diabetes (by glucose tolerance test). (3) using any kind of hypoglycemic drugs.The differences between shift workers and day workers on demographic characteristics and clinical indexes were compared using Student-t test for continuous variables and Chi-square test for categorical data. To compare the relationship between shift work duration groups and DM, we used logistic regression.Results:For relationship between shift work duration and DM, a total of 26,463 retired workers were included in this analysis, the fundamental characteristics were the same with section one in part one. The ORs of DM increased as shift work duration extended. The multi-variate adjusted ORs (95% CI) were 0.99 (0.81-1.20),1.14 (0.98-1.32),1.23 (1.12-1.36) and 1.25 (1.15-1.37), P trend value was 0.000. Stratified analysis according to leaving shift work duration was very interesting. For people worked in shift position less than 20 years, the ORs decreases as leaving shift work duration increased, while in participants working for 20 or more years in shift, the association remained consistency.For relationship between types of shift work and DM, this study included 9,513 participants, among which 2,366 were shift workers. Baseline characteristics were similar with that in section two of part one. Compared with day workers, three shifts were related with DM significantly, but not two shifts. The adjusted OR (95% CI) was 1.34 (1.12-1.59). And the relationship was partially modified by age, sex, BMI and smoking status.Conclusion:Shift work was related with DM, and the association was strengthened by older age, high BMI and smoking habit. Leaving shift work duration partially modified the relationship between shift work and DM. Three shifts increased the prevalence of DM in retired workers, but two shifts did not. And the relationship of three shifts and DM was modified by age, sex, BMI and smoking status.This was a large population based study of Chinese retied workers in a motor manufacturing company. Basing on shift work related health impact, we investigated the association between shift work duration, leaving shift work duration, and different types of shift work with sleeping quality, metabolic syndrome, diabetes in retired workers. The innovations of this study are as follows:(1) to explore the relationship between shift work and sleeping quality, metabolic syndrome, diabetes in retired workers in China for the first time, verified the persistence impact of shift work on sleep and metabolic disorders; (2) to discover the influences of leaving shift work duration on the association of shift work with sleeping quality, metabolic syndrome and diabetes; (3) to discuss the difference of three types of shift work on sleeping quality, metabolic syndrome and diabetes of retired workers. |
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