## 3 Results
### Results of Eligible Studies  
All eligible studies examined the correlation between SW and telomere length correlated with other outcomes (sleep duration, inflammatory response, breast cancer risk, psychosocial in workplace, occupational well-being, work capacity, oxidative damage). All studies were carried out in healthcare workers (mostly in nurses).  
[PERSON] and colleagues [54] found that sleep period was positively correlated with telomere length between nurses less than 50 years old, and SW is a risk factor to have shorter telomere lengths.  
In detail, [PERSON] and colleagues [54] in 4117 female workers from the \"Nurses' Health Study\" underlines a significant positive correlation between sleep period and telomere length was underlined between women under the age of 50 (\(p\) = 0.004), but not among those over 50 (\(p\) = 0.33). Besides, they highlighted that women with a more extended chronicle of rotating night shifts were inclined to have shorter telomere lengths.  
An in-depth study conducted on cell culture, mice, and humans highlight that telomerase activity shows endogenous circadian rhythmicity in humans and mice, and _CLOCK_ deficiency causes a loss of telomerase activity [55]. Moreover, workers with standard work have circadian oscillation of telomerase activity; instead, shift workers lose the circadian rhythms of telomerase activity [55].  
The investigation carried out by [PERSON] et al. [56] suggests a probable role of Long Pentracin 3, an acute-phase protein, an inflammatory process due to SW. Furthermore, SW is correlated with short telomere length and with increased systemic inflammation (coefficient = 0.15; \(p\) = 0.033), so those shift workers are more susceptible to premature aging [56].  
In a nested case-control study carried out in Norwegian nurses, telomere shortening is correlated with the interval and strength of night work and may be a co-factor for breast cancer risk between female shift workers [57]. Telomere length was assessed from 563 breast cancer of shift workers and 619 controls. [PERSON] et al. [57] demonstrate that telomere length is affected by intensive SW, as work with six successive nights for more than 5 years was correlated with decreased telomere lengths (\(-3.18\), \(95\%\) CI: \(-6.46\) to \(-0.58\), \(p\) = 0.016). Telomere shortening is also correlated with a rise in breast cancer risk in workers with long periods of successive night shifts. Therefore, workers among longer telomere lengths had a lesser risk for breast cancer if they had worked more than four (OR: 0.37, \(95\%\) CI: 0.16\(-\)0.79, \(p\) = 0.014) or five (OR: 0.31, \(95\%\) CI: 0.10\(-\)0.83, \(p\) = 0.029) consecutive night shifts for 5 years or more.  
[PERSON] and colleagues [58] demonstrated that a favorable workplace and work-related health might control the correlation among age and telomere length. Moreover, the authors indicated the potential application of telomere length as a biological measure of age [58].  
In other research, [PERSON] and colleagues [59] discovered that SW promotes overbalanced oxidative stress reaction that might induce premature aging; the results show that lung function was negatively associated with higher levels of urinary 8-oxoGua (\(p\) = 0.005) and shorter telomere length (\(p\) = 0.049).  
An investigation carried out by [PERSON] et al. [60] underlines a correlation between extended exposure to SW and molecular modifications that might be implicated in the process, for example, cellular aging. They found an increasing between telomere length and several years in SW in workers in SW \(<\) 12 years (0.06 (0.03; 0.09), \(p\) < 0.001), while a reduction if work was involved in SW \(\geq\) 12 years (\(-0.07\)\(-0.10\); \(-0.04\)), \(p\) < 0.001), but this does not clarify the average number of nights made by workers.  
However, all these studies underlined a shortening of telomere length in correlation with SW and with aging in shift workers.