Salāmat-i kār-i Īrān (May 2020)
The effect of workplace and unusual working hours on dry eye symptoms of petrochemical industry workers
Abstract
Background and aims: Dry eye is one of the most common symptoms among patients who seek for ophthalmologic examination. For this reason, causes, management, methods and the effect of this disease on patients’ quality of life have been broadly studied over the last few years. In this multifactorial disease, ocular surface and tear film are affected which results in instability of tear film and ocular discomfort. There are some risk factors for dry eye disease (DED) including age, gender, systemic medications, autoimmune disorders, low humidity environments and contact lens wear. Information on DED causes may improve diagnosing and managing of this debilitating, chronic condition. In addition to its ocular sign and symptoms, dry eye disease not only has an effect on patients’ visual, social and occupational quality of life, but also patients’ life style can affect the state of this disorder. Among risk factors affecting life style, environmental and occupational factors have been proved to change pre- corneal tear film so that high temperature and low humidity can increase aqua evaporation and lead to ocular discomfort. Indoor and outdoor air pollutants result in visual disturbances due to ocular irritation and DED. Additionally, some personal habits such as sleep quality can also affect tear film stability. In a study which was performed in Japan, a sleep questionnaire was used to subjective measurement of sleep quality and quantity. Their study population were normal office workers. They found that sleep quality consisting: sleep duration, medication, latency or disturbances, is associated with dry eye symptoms. A recent study has shown the effect of sleep position on the ocular surface, so that sleeping in supine position may reduce the symptoms in dry eye patients. Ocular discomfort due to DED may result in ocular fatigue which increases the need of patients for more break times and deterioration of working performance and human faults. Given that not trying to alleviate eye symptoms caused by DED, can have a bad effect on individuals’ performance in workplaces, recognizing the effective factors on eye dryness is very important. Objective: This study aimed to find a relationship between working in petrochemical plants, unusual working hours and dry eye symptoms in petrochemical frontline employees. In this work, we compared a population of petrochemical industry night and day workers with a normal group, in order to assess potential relation of their working environment and sleeping time on their dry eye symptoms. Performing a study on this group of participants allows us to simultaneously assess the effect of outdoor air pollution and working shift on patients’ objective and subjective dry eye signs and symptoms. Identification of key risk factors for DED in symptomatic group can be helpful in better management of this condition. Methods One hundred ninety five males were recruited in this study, and divided into two groups: workers (petrochemical night and day workers) and non- workers (control) group. Day and night workers were working in day and night- time shifts at least for more than 1 year and they had no rotating shifts. Participants with any history of ophthalmic or systemic diseases or ocular surgeries, taking medications which induce dry eye or worsen dry eye symptoms, smoking, contact lens application, lack of sleep (less than 7 hours night sleep for control and day worker groups and less than 7 hours day- time sleep for night workers) and computer users for more than 6 hours a day, were excluded. Socio – economical demographics such as educational level and working experience and salaries were considered. All dry eye examinations were performed in the morning (at least 2 hours after waking up) for day time workers, and in the afternoon (at least 2 hours after a day time sleep) for night workers. Working hours was the same for workers (12 hours working in the field: 8 AM- 8 PM for day time and 8 PM-8 AM for night- time workers). Participants were compared in terms of Schirmer’s test I (without anesthesia), tear break up time (TBUT) and subjective dry eye symptoms (based on DEQ-V questionnaire). The TBUT recorded as the number of seconds that elapse between the last blink and the appearance of the first dry spot in the tear film. A TBUT under 10 seconds was considered abnormal. For Schirmer’s test the amount of moisture of paper strips were measured and less than 10 mm of moisture in 5 minutes was considered as abnormal. DEQ- V questionnaire consists 5 items for the presence of 3 symptoms of dry eye including: watery eyes (frequency), discomfort (frequency, AM &PM intensity and bother) and dryness (frequency, AM &PM intensity and bother). Other 2 items were: whether the participants have told to have dry eye or they think they have it. The validity of this questionnaire has been evaluated by Chalmers and a total of DEQ score more than 6 can be an indicator of dry eye and needs further clinical tests to confirm DE. Patients with a score of >12 should be referred to be ruled out for Sjӧgren’s Syndrome. After explaining the nature of the study, an informed consent was obtained from each participant The research was approved by the Research Ethics Committee of Mashhad University of Medical Sciences and the protocol adhered to the tenets of the Declaration of Helsinki. Results: Sixty-five non- workers (control group) and 130 workers (65 night and 65 day- workers) were enrolled in the study. Statistical analysis was performed using SPSS software for Windows version 16 (SPPS, Inc. Chicago, IL). Student t-test and one way analysis of variance (ANOVA) were used to compare means of Schirmer’s test, TBUT and DEQ score among groups. Pearson χ2 test was performed to compare the percentage of abnormal cases in each group. Bonferroni post hoc corrections were applied for multiple comparisons. For all results p<0.05 was considered as statistically significant. Mean age of participants was 37.44±3.87 years (range 30-45 years). For a better between groups’ comparison considering working shifts, workers were divided in to night and day shift groups and comparison was performed between 3 groups. According to our results, 3 groups were not significantly different regarding age, educational level and working experience (p= 0.218, p=0.884 and p=0.378, respectively). One way ANOVA test showed a significant difference of TBUT between 3 groups (p=0.007). In pairwise comparison, we found that mean TBUT (in seconds) was significantly different between control group and night workers (p= 0.005), but there was no difference between controls and day workers (P=0.181). Although it was greater in day workers, TBUT was not markedly different between night and day workers (P=0.588). Our results showed a significant difference for Schirmer’s test between 3 groups (p<0.001). Multiple comparison of means between groups showed a statistically significant difference between control group and day workers (p=0.002), and also between control group and night workers (p<0.001). The result of the Schirmer’s test between night and day workers was not significantly different (p=0.509). Mean DEQ score was also significantly different between groups (p<0.001) and it was higher in night shift workers. In between group comparison, mean DEQ score was significantly different between controls and night workers (p<0.001). However, mean DEQ score was not markedly different between controls and day- workers or between night and day workers (p=0.053 and p= 0.180, respectively). But it was significantly different between control group and night- workers (p=0.009). The percentage of abnormal findings in all the tests was higher among night workers. However, 3 groups were significantly different just for abnormal DEQ score (P= 0.0.26). Also, in 2 group comparison between workers and non- workers, there was a significant difference in Schirmer’s, TBUT and DEQ results (p<0.001, p=0.004 and p=0.001, respectively). Conclusion: Both day and night time workers who participated in our study were exposed to pollution from open field petrochemical plants. Day workers’ activities are in higher temperature working hours. On the other hand night shift workers work in lower temperature hours but sleep in unusual hours during the day. This can be the other justification for the lack of significant differences between the results of day and night time workers. Although we recruited participants with at least 7 hours a day sleep but we did not have information about sleep quality of worker and non-workers. Incorporating a sleep quality questionnaire for volunteers can help us to find out if, there is actually any difference in sleep quality of participants in each group besides abnormal sleeping hours. More comprehensive studies on larger population may potentially result in more significant differences among groups. Adding some other dry eye tests including osmolarity test and Ocular Surface Disease Index score to future studies can also be valuable. In addition, recruiting non- residents as control group can better confound intervening factors and results to a more precise comparison between worker and non- worker groups. Working in petrochemical industry plants has an effect on symptoms of dry eye disease in frontline workers. On the other hand, long term working in night shifts seems not to be a key factor for DED. However, these factors should be considered occupationally in order to improve the employees’ performance in workplaces.
