Being self-employed is the only factor associated with a lower risk of sick leave for low back pain over the next 18 months, and a lower risk that, if it occurs, it will lead to 30 or more days of leave during that period. This is the conclusion of a scientific study on sick leave due to low back pain in Spain and endorsed by the journal Occupational and Environmental Medicine.
Low back pain is one of the leading causes of disability and work absence worldwide, and its onset and progression are influenced by biological, clinical, sociodemographic, and psychosocial factors. This study analyzed which factors are associated with requesting sick leave for low back pain and its duration in Spain, with the aim of developing predictive models to anticipate which workers are most likely to request it and for how long, and identify those in whom preventive measures should be applied as a priority.
The researchers analyzed 77 factors that previous studies had shown to be associated with pain intensity, the degree of disability, and the evolution of both parameters, including sociodemographic aspects (such as age, sex, or education level), clinical aspects (such as pain intensity, duration and aggravating factors of the pain, or the presence of radicular pain), psychological aspects (such as the use of anxiolytics and antidepressants, the intensity of catastrophizing thoughts, or the fear of losing one’s job), occupational factors (such as self-employment or being an employee, the type and duration of the contract, or the physical demands of the job), and economic factors (such as income level, the share of fixed versus variable components, or the impact of a potential sick leave on them).
The conclusions of the study show that, among all those variables, the only one associated with both a lower risk of sick leave and, if it occurs, fewer days off is that the worker is self-employed (as opposed to working as an employee). According to the authors, this could be explained because in the Spanish Social Security system self-employed workers face greater income instability and fewer benefits during temporary incapacity than employees. Nonetheless, it is striking that this aspect is more relevant than all the other clinical, biological, psychological, economic, and occupational parameters.
Low back pain common among the working population
It is also noteworthy that, although 57% of workers reported some discomfort or low back pain and 60% were taking medication for this reason, only 7.4% requested sick leave for this cause over the next 18 months. This suggests that low back pain is very common among the working population, but only prompts leave when it is disabling or when other factors coexist.
The Prof. Jesús Seco, of the Institute of Biomedicine of the University of León and the University of the Basque Country, and co-author of the study, highlights “the arduous effort involved in collecting data from more than 7,000 workers and following their sick leaves and causes for 18 months,” as well as “the collaboration of many physicians in the National Health System with private entities, such as workers’ compensation insurers and large companies, without which this research would have been unviable.”
The Dr. Ana Royuela, of the Clinical Biostatistics Unit of the Puerta de Hierro–Segovia Integrated Medical Research Institute, a member of the Consorcio Centro de Investigación Biomédica en Red, Área Epidemiology and Public Health (CIBERESP), and co-author of the study, notes that “it is striking that the vast majority of clinical parameters that have demonstrated influence on pain progression or disability turn out to be irrelevant for predicting sick leave or its duration. That reflects that requesting or maintaining sick leave is a behavior in which the biological component is only one aspect among others, and not the most determinant. The data suggest that, all else equal, a self-employed person continues to work when an employee requests sick leave.”
For its part, the Dr. Francisco Kovacs, of the Kovacs Back Clinic at HLA University Moncloa Hospital, director of the Spanish Network of Researchers in Spine Ailments (REIDE) and co-author of the study, emphasizes that “in practice, this study suggests that strategies for preventing low back pain and the associated sick leaves should be directed at the entire working population, since it is impossible to predict who has a higher risk. This argues for prioritizing strategies that, in addition to being effective, have proven more efficient.”
Predictive factors for sick leave due to low back pain
The predictive factors that have shown a significant association with a higher risk of taking sick leave for low back pain are:
- Being an employee. The probability that a self-employed person will request sick leave for low back pain is 33% lower than that of an employee.
- Age: for each additional year, the risk increases by 3%.
- Duration of prior episodes: sick leave is 43% more likely among those who have previously had low back pain episodes lasting more than 14 days, compared with those who had shorter episodes or none.
- Personal expectations: sick leave is 44% more likely among those who expect that they are likely to have it in the coming year.
- Perceived economic impact: sick leave is 48% more likely among those who perceive that it would cause a significant economic harm.
- Job insecurity: sick leave is 30% less likely among those who feel their job is at risk.
On the other hand, the main factors predicting a higher risk of accumulating 30 or more days of sick leave over the next 18 months are: being an employee and feeling low back pain when lying in bed.
Statistical analyses showed that, while each of these parameters is associated with risk of leave or duration, they do not reliably compute the individual risk for a given worker. This reinforces the need to apply preventive measures to the entire working population.
