Factors in the workplace that increase the chances of
Developing Sciatica and requiring hospitalization

Sciatica is a frequently occurring musculoskeletal condition, affecting approximately 2-5% of the population, depending on various factors. It leads to significant societal healthcare expenses and imposes a substantial burden of disability on individuals afflicted by this condition.

Previous research has identified connections between work-related factors and conditions such as herniated lumbar disc or sciatica. However, our understanding of the relationship between work-related factors and the risk of sciatica has not significantly advanced in recent years.

Numerous earlier studies have explored work-related factors using cross-sectional or case-control study designs, which can introduce recall bias in assessing workload exposure.

In these study designs, individuals with sciatica may have opted for less physically demanding work tasks, and the influence of the “healthy worker effect” may have affected the findings.

Engaging in physical activity during work and being exposed to occupational workload, such as lifting or carrying heavy objects, have been linked to a higher likelihood of developing sciatica.

Similarly, non-occupational activities involving lifting, particularly when performed with a straight knee and a bent back, have also been associated with an increased risk of herniated lumbar disc.

Twisting of the trunk during work and occupational exposure to whole-body vibration, such as experienced by motor vehicle drivers or machine operators, have been proposed as potential risk factors for sciatica.

However, the role of physically heavy labor as a definitive risk factor for sciatica has been debated in some prospective studies, with inconsistent findings.

In a study reported by literature, involving 3,891 participants, it was found that 75% of them identified their present or most recent occupation as the longest in their work history.

The average duration of this longest occupation was 17.0 years, with a standard deviation of 9.5 years. For the remaining participants, their longest occupation had an average duration of 12.4 years (SD 6.7), while their present or last occupation lasted for an average of 4.6 years (SD 3.3).

During a follow-up period encompassing 111,416 person-years, a total of 120 participants required hospitalization due to sciatica. The primary ICD codes associated with these hospitalizations varied over time.

Prior to 1986 (Eighth ICD Revision), the most common codes were 725.10 (lumbar intervertebral disc displacement) with 28 cases and 353.99 (sciatica) with five cases. Between 1987 and 1995 (Ninth ICD Revision), the prevailing code was 7227C (intervertebral disc disease with myelopathy,

Syndroma ischiadicum), accounting for 43 cases. From 1996 onwards, the leading codes shifted to M51.1 (lumbar intervertebral disc disease with radiculopathy) with 24 cases and M54.3 (sciatica) with seven cases.

Smoking is connected to a higher risk of sciatica. Sedentary occupations that involve handling relatively heavy objects and physically light moving/standing jobs are associated with an increased likelihood of hospitalization for sciatica.

Conversely, physically demanding work seems to have a protective effect against sciatica. Specifically, occupations involving lifting or carrying heavy objects and exposure to vibration significantly predict the risk of developing sciatica.

On the other hand, factors such as awkward trunk posture, prolonged standing or sitting, and paced work do not show a significant association with the occurrence of sciatica.

Current smoking and frequent lifting were associated with an increased risk of hospitalization for sciatica. Sedentary work involving the handling of fairly heavy objects or physically light work showed a higher risk, while heavy or very heavy work predicted a reduced risk of hospitalization for sciatica.

There was a notable interaction between excess body weight and exposure to whole-body vibration, which influenced the risk of hospitalization for sciatica. Overweight and obese individuals who were exposed to vibration in their workplace had a significantly higher risk of being hospitalized for sciatica.

However, there was no increased risk observed for overweight or obese individuals who were not exposed to vibration, nor for normal-weight individuals who were exposed to vibration.

A cross-sectional study reported by literature conducted a generation ago, called the Mini-Finland Health Survey, reported the prevalence and determinants of sciatica and other low back syndromes.

Our current cohort study, based on this survey, revealed that lifting or carrying heavy objects at work, sedentary work involving fairly heavy objects or light physical activity, and exposure to whole-body vibration were predictive of developing sciatica requiring hospitalization during a 30-year follow-up.

Interestingly, heavy or very heavy work was associated with a reduced risk of hospitalization for sciatica. Obese individuals exposed to vibration at work faced a significantly higher risk of hospitalization for sciatica, while BMI or vibration alone did not have predictive value.

Previous research has consistently shown that physically demanding work increases the risk of developing sciatica. However, a study conducted among middle-aged employees in Finland did not find the same association.

In the current study, it was observed that sedentary work involving the handling of fairly heavy objects or physically light work involving standing or moving was predictive of developing sciatica.

Surprisingly, engaging in heavy or very heavy physical work was associated with a reduced risk of hospitalization for sciatica. These findings suggest that individuals with poorer physical condition may opt for lighter work tasks, explaining the increased risk observed in those occupations.

Conversely, individuals with better physical fitness and muscle condition may have improved control of the spine and trunk, which could contribute to the lower risk observed in physically demanding occupations.

Another possible explanation for the reduced risk is that individuals in physically heavy work have better tissue tolerance. It is important to consider the potential influence of the “healthy worker effect” in occupational studies, as individuals with poor health may be excluded from the workforce, potentially affecting the study outcomes.

A study reported by literature did not identify a significant association between obesity and hospitalization for sciatica. However, it did find that the combination of obesity and occupational exposure to vibration increased the risk of sciatica.

This finding contradicts earlier studies that have reported a link between overweight/obesity and sciatica. One possible explanation for the lack of association in this study is the exclusion of the non-working population from the analysis. It is worth noting that individuals who are unemployed have a higher likelihood of being overweight or obese compared to those who are employed.

While earlier studies reported by literature have associated sitting with the emergence of low back disorders, few have specifically focused on sciatica. Many studies examining the prevalence of sciatic pain in occupations involving sitting also involve co-exposure to awkward postures and vibration.

The higher intradiscal pressure associated with sitting may contribute to sciatica in sedentary occupations. However, in the current study, sedentary work involving the handling of fairly heavy objects was found to predict the risk of hospitalization for sciatica, whereas sitting exposure alone did not show a significant association.

Consistent with previous studies, our findings demonstrated that lifting and carrying heavy objects were associated with an increased risk of sciatica leading to hospitalization.

This relationship can be explained by the fact that lifting and carrying tasks contribute to higher intradiscal pressure and can potentially lead to structural failure of the intervertebral discs. In our study, the questionnaire assessed the physical strenuousness of work, which included lifting and carrying heavy objects, while also separately analyzing it as a specific exposure.

This overlap in the questionnaire sections may have influenced our results, although we obtained information on both general strenuousness and specific exposures at work independently.

Previous studies reported by literature have found associations between vibration exposure and back pain, including sciatica. Occupational exposure to vibration, particularly while sitting, has been linked to a higher risk of sciatica.

In our study, vibration exposure did not significantly predict hospitalization for sciatica overall, but overweight or obese individuals exposed to vibration at work had a higher risk.

Smoking at baseline was found to predict the occurrence of sciatica, likely due to its impact on intervertebral disc nutrition and pro-inflammatory cytokine production.

The highest risk of hospitalization for sciatica is observed among overweight or obese individuals exposed to whole-body vibration, involved in lifting or carrying heavy objects, or engaged in sedentary occupations that require handling fairly heavy objects.

Conversely, heavy or very heavy work appears to be protective. However, further research is needed to confirm the effect modification of obesity on vibration exposure and to determine the causal implications and potential preventive measures.