Prevalence of sleep disorders among shift and day workers in industrial workers of North Guwahati, Assam

INTRODUCTION

Sleep disorders are highly prevalent in industrialized societies. Shift work interferes with onset, maintenance and consolidation of sleep. It thus conflicts between day oriented circadian physiology, homeostatic sleep regulatory process and sleep functioning, thereby increasing the risk of sleep disorders leading to health problem like stressful social and familial conditions, cardiovascular disease, accidents and cancer.¹ Sleep-disorders are highly prevalent in industrialized societies. Variability in the symptomatology in sleep disorder is related to difference in the amount or quality of sleep obtained by individuals engaged in various types of shift work. Insomnia is the primary symptom and is the minimal criteria for sleep disorder, but it is not that unique.² Realizing the magnitude and huge economic impact, sleep medicine is an established discipline in developed countries. In India it is a new discipline practiced only in metropolitan cities. Research have been conducted only on a sparse proportion of the population.³ The study was conducted to estimate the prevalence of sleep disorder among shift and day workers in industrial workers of North Guwahati, Assam.

METHODS

This was a institution based cross-sectional study conducted among industrial workers of North Guwahati, Assam from July-December 2021. Informed consent was taken after it was translated in local language. The pilot study assessed the feasibility and applicability of the questionnaire in 30 individuals and estimated problems in response. Based on studies done by other authors assuming prevalence of general sleep disorder to be 39% and 24.6% in shift and day workers 95% CI and 80% power the number of subjects estimated is 161 for each group using the following formula:¹

n=( Z_a/2 + Zβ)² *[P₁(1-P₁)+P₂(1-P₂)]/(P₁-P₂)²

Inclusion criteria

All subjects scheduled for shift and day duty were included. Shift work and day work timing taken were (6 am-2 pm) (2-10 pm) (10 pm-6 am) and (7 am-3 pm) respectively.

Exclusion criteria

Subjects who knew that they have sleep disorder and were on treatment. Subjects who did not give consent. Subjects were drawn from 16 industries, 10 subjects from each industry. Selection was done by simple random method. 2 extra sample were selected, one from the first industry and the other from the last industry. The 322 subjects were interviewed using pre-tested and validated proforma. GSAQ (2002) questionnaire was used which comprised 11 sleep items constructed as a question next to row of checkbox response options regarding symptom frequency over the last four weeks (never, sometimes, usually and always). It is presented on a single paper.

Header contains patient details and lays out symptom’s complaints within a grid with easy patient response and clinical interpretation. It includes four of the six sleep disorders i.e., Insomnia, OSA, RLS and parasomnias based on ICSD criteria. Presence of any one or more of the above sleep disorders were considered to be having general sleep disorders.³ Questions were put to the respondents after detailed explanation on the study. No clinical evaluation nor any lab investigation was undertaken during the study.

RESULTS

The study includes 322 subjects. Most of them were from Assam while few of them were from West Bengal, Bihar and Uttar Pradesh. Table 1 shows socio demographic data for the two work groups.

Mean age of the respondents was 35 and 39 years for shift and day workers respectively. Percentage of male was 68% and 51 % for shift and days workers respectively. Presence of partner was almost similar in both the groups. Workers were mostly higher secondary or degree passed.

(P)- sleep disorder present, (A)- sleep disorder absent.

Group difference were found for insomnia, restless leg syndrome and parasomnia.

Prevalence of general sleep disorder was 34% (55) in shift and 19% (30) in day workers. The difference was statistically significant as shown (Table 3).

DISCUSSION

The study shows mean age of the respondents was 35 and 39 years for shift and day workers. Presence of partner and children at home were almost similar for both the groups. The characteristics of the group were similar to the study done by Kerkhof.¹ It adds to findings of previous studies by showing that shift work compared to day work is associated with higher prevalence of ICSD defined sleep disorders. Though the prevalence was much higher compared to study done by Kerkhof and Drake.^1,2 In contrast to our study, study done among a healthy population in South India showed a higher prevalence of Sleep Related disorders.^6,9 Prevalence of insomnia was higher in shift workers (17.39%) compared to the day workers (9.3%). This finding matches the findings of study done by Drake but it is much higher compared to study done by Kerkhof.^1,2 Additionally the prevalence of restless leg syndrome was more in shift workers (14.28%) compared to day workers (8.07%), which adds to the findings of other authors.¹ Obstructive sleep apnea in shift workers is 34.16% and 6.21% in day workers. This is much higher compared to study done by Kerkhof, which shows prevalence rate of sleep related breathing disorder to be 6.8 in shift workers and 6.1 in day workers.

The study supports the view that shift work has affect on sleep pattern thus leading to sleep disorder. Additional studies are needed to determine the mechanism responsible for individual vulnerability to the negative consequences of shift work.

The present study reveals the prevalence of sleep disorders to be higher in shift workers than day workers in the industrial population. Lack of awareness is a major influencing factor. Thus, awareness on the importance of sleep hygiene as well as widening the subject of sleep medicine by including the industrial workers would be helpful to the decrease the morbidity related to the shift work.

Limitations

Sleep problems assessed in this study is only through questionnaire. It is not supported by any clinical examination or laboratory tests. The problem of sleep disorder might be more than the study results. Secondly, this was a cross-sectional study based only on the previous 4 weeks period. This might have the problem of recall bias. Moreover, findings by the use of only questionnaire might not be representative of the general sleep disorder. At last, to compare data between different studies in different regions is not completely effective due to variability in operational definitions and different measures/ questionnaires used to evaluate sleep.

CONCLUSION

Use of questionnaires is one of the easiest cost-effective tools, that can be utilized at field level for assessing prevalence at large scale. Shift work have a profound effect on sleep, starting from the most common disorder like insomnia to rare instances like restless leg syndrome. This disorder causes misalignment between the circadian cycle and the work schedule. Sleep medicine might be helpful to improve the sleep hygiene especially among the shift workers to improve the sleep pattern. Additional research is needed to determine the prevalence among general population, day workers and shift workers so as to develop countermeasures for the sleep disorders.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

REFERENCES

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