INTRODUCTION

Low back pain is one of the most common conditions in musculoskeletal pathologies, affecting the lower back area, and can occur at any age, gender, and social stratum. Generally, it has a benign course and its interest is focused on its high frequency, social, labor and economic repercussions¹. It is characterized by pain that presents itself in an acute form and over time can become chronic, it can also generate some degree of functional limitation and even lead to the impossibility of making any movement². Pain in the lower back is one of the most common reasons of medical consultation and medical rest worldwide. It is said that low back pain affects eight out of ten people and, according to studies, it can hurt people's quality of life, affecting their work activities and even their daily activities³.

Low back pain has a high prevalence because it affects a large number of people around the world. 80% of the population will suffer from low back pain at least once in their lifetime¹, and even more, people who use their musculoskeletal system to carry out physical activities such as marines who are constantly subjected to high physical loads due to the high demand for training they exercise. In addition to certain risk factors that amplify the possibility of suffering from this condition. The low back pain is one of the musculoskeletal disorders that causes the greatest disability in the Armed Forces⁴. For this reason, documenting the variable behavior such as age, gender, military service time, overweight or obesity and dyslipidemia, leads us to awaken interest to investigate this problem⁵.

The idea of investigating low back pain and its risk factors will allow us to transmit a knowledge base on this subject, identifying the factors that increase the risk of suffering it, as has been explained above. This study aims to identify the risk factors of low back pain in marines attended by the outpatient clinic of Naval Medical Center Lima in 2017.

METHODS

An analytical, observational and retrospective case-control study was conducted. The sample was composed of active naval personnel (sailors), 66 with a diagnosis of low back pain (cases) and 132 without low back pain (controls) attended by the physical medicine and rehabilitation outpatient clinic of the Centro Médico Naval hospital, where patients over 18 and under 70 years old are treated. The sample was selected at random.

Data were collected from clinical records in the hospital's Clinical Archives Unit comprehensively and thoroughly, discarding clinical records with incomplete information and illegible handwriting.

The dependent variable was the diagnosis of low back pain registered in the clinical history. The independent variables were age, length of service, gender, nutritional status above normal parameters according to BMI (overweight and obesity) and the presence or absence of dyslipidemia.

The data were collected through a data collection sheet and then transcribed into a computer database in Excel 2010 to do this research study.

The chi-square test, with 95% confidence intervals, and the p-value were used for statistical analysis. Logistic regression was used to estimate ORs. Relative and absolute frequency distributions were also presented. Data processing was performed with SPSS 24 and Excel 2010 software.

RESULTS

Of the total population, there were 66 cases and 132 controls, the most common gender was male with 179 individuals representing 90.4%, the median age was 26 years (36-77 years), 99 patients attended were overweight and 32.8% presented dyslipidemia. All this can be seen intable 1.

In the bivariate analysis of factors associated with low back pain were overweight / obesity, dyslipidemia, age and time of service. The p-values and their ORs can be seen intable 2.

In the multivariate analysis, only overweight/obesity and dyslipidemia were associated factors for the presence of low back pain in seafarers (table 3).

DISCUSSION

Low back pain is a very common musculoskeletal condition worldwide⁶. Although it is a benign pathology that in most cases remits spontaneously, there is a group in which it can persist over time³, becoming chronic or affecting the quality of life of those who suffer it and their job performance⁷. There are risk factors that favor the presence of low back pain, some of which are influenced by ergonomics, among other factors; however, there are few national and international studies on low back pain and the risk factors associated with it in the military population, which is also prone to this condition because of the type of work they do during their military career⁸.

It is important to recognize the risk factors that increase the likelihood of suffering from low back pain, especially the most common ones, such as age, gender, and overweight or obesity. In the Naval Medical Center Hospital, these factors were evaluated in the period from January to December 2017, as well as other factors such as time of military service and dyslipidemia, a variable in which association has been found as a risk factor for low back pain in some studies.

In our study, only in the bivariate analysis, a significant and inverse association was obtained between age and low back pain, being the young adult population the most affected. This result agrees with several studies carried out in military populations; such as the one described in Honduras, where the most frequent age group was from 31 to 45 years old⁹, in Ecuador, where the most frequent age group was from 30 to 39 years old, with 49 %¹⁰, and in the United States, it was found that the incidence ratio for the age group over 40 years old in comparison with the group from 20 to 29 years old was 1.28 (95% CI: 1.27-1.29)¹¹These results are the opposite of what we found.

As for the studies that were carried out in the Peruvian military population, we have Bernedo Llerena A, who specified that in his study population, the average age was 34,2 years¹¹, the study of Tejada EJ, where it was found that the frequent age range where low back pain occurred was between 40 and 49 years (39,45%)¹², the study of Cáceres Álvarez ME, where it was found that ages ranging from 41 to 60 represented 42.31%¹³, and finally the study of Ramírez Köhler S, where it was specified that the average age of patients with low back pain was 41.4 ± 4.45¹⁵.

On the other hand, there are studies in which young age predominates in the military with low back pain, like the study carried out in Ecuador, where the most frequent age range was from 23 to 27 years because young people are subjected to more demanding training¹⁵and the study of Rodríguez Vargas DM carried out in Arequipa where it was found that the most frequent age range was between 18 and 20 years, with 88%¹⁶.

Concerning the sex factr, in the bivariate analysis the obteined predominance in males, but not in the multivariate, unlike the results of other studies where it was predominantlymale, as in the studies of Macías DD with 90.4%¹⁰, Pinto Romero MR et al. with 60.1%⁽⁸⁾and many other authors^12,13,14,16. This may be because these studies were carried out in a military population where the prevalence of males was higher than the prevalence of females.

In our study, there was no association between low back pain and gender as the results were not significant. This contrasts with what was found in an American study where it can be observed that women in comparison with men had significanlly higher incidence rate for low back pain, of 1.45 (95% CI: 1.44-1.46)¹¹. Concerning the variable military service time, it did not prove to be statistically significant, therefore no association was found between military service time and the presence of low back pain. This contrasts with the study carried out in Arequipa, where it was evident that the highest percentage of patients with low back pain (43%) were between 6 and 12 months in military service, 31% had less than 6 months and 26% had more than 12 months in military service¹⁷. Another cross-sectional study was carried out in Canada, it was found that older police officers had a higher prevalence of chronic low back pain (adjusted OR, 1.06; 95% CI, 1.01-1.12)¹⁸.

Regarding overweight or obesity, our study found that most patients with low back pain had a body mass index (BMI) above the parameters of normality, so it was statistically significant. This means that the BMI is associated with the presence of low back pain, so people who have a BMI higher than the normal range have a greater risk of suffering from it. This is comparable to the research of Ramírez Köhler S, who through a transversal study, found that 54.3% of patients with low back pain were overweight and so it was considered a risk factor for the development of low back pain¹⁸. Likewise, in the study by Bernedo Llerena A, it was described that 35.97% of military personnel were overweight and 7.19% were obese¹¹.On the other hand, Shiri R. et al. performed a meta-analysis of 33 studies where it was demonstrated that the obesity condition increased the risk of suffering from low back pain in 12 months (OR: 1.53; 95% CI 1.22-1.92)¹⁹.

Finally, as for the dyslipidemia variable, it was found that this is a factor associated with low back pain, so anyone who has lipid disorder is more likely to occur. This result is compatible with a study carried out in Finland, as the results were positive after an analysis of triglycerides and serum cholesterol in patients with localized or diffuse chronic low back pain²⁰Years earlier, this finding was also referred to in a prospective study in the United States, in which they document a positive association between the concentration of triglycerides and low back pain referred by retired patients who have worked as office workers²¹. Citko et al. found that hyperlipidemia increased the risk of low back pain in medical personnel by up to 8 times²².

A study was carried out in Mexico, in which it was found that the absence of dyslipidemia had a protective effect (OR 0.26, 95% CI: 0.12 to 0.56) as the absence of dyslipidemia reduced the risk by up to 74% according to the OR expressed by the logistic model; in other words, the presence of any type of dyslipidemia would be a risk factor for chronic low back pain¹⁹.

If it is accepted that there is an association between dyslipidemia and low back pain, it could be sustained pathophysiologically through the development of atheromatosis in the lumbar arteries. This effect would be given by the reduction of the blood supply to the lumbar region which would induce degeneration of the vertebral discs, giving changes in their anatomy²⁰, in other words, atherosclerosis of the lumbar vessels has been suggested as a mechanism that leads to lumbar pain¹⁹.

The limitations of the present study lie in its design of cases and controls as low back pain is a relatively common disease but of slow appearance, so it would be advisable to carry out subsequent cohort studies to determine the risk factors in the military population.

CONCLUSION

It is concluded that low back pain in active naval personnel at the Naval Medical Center hospital is associated with overweight / obesity and dyslipidemia.