Prevalence and risk factors analysis for low back pain among occupational groups in key industries of China

With the development of science and technology and the acceleration of industrialization, significant changes have taken place in the working modes of workers. Workers generally suffer from work-related musculoskeletal diseases (WMSDs) caused by adverse ergonomic factors, such as repetitive operation, bad working posture, excessive force load, continuous muscle tension, and vibration contact. The World Health Organization defines this as “the health problems of muscles, tendons, bones, cartilage, ligaments, nerves, and other motor systems caused or aggravated by work activities, including all forms of health disease states from minor and short-term injuries to irreversible and incapacitated injuries.” Particularly, low back pain (LBP) is the most common condition.

Research shows that [1] about 80% of people globally have experienced LBP. It brings great pain to people, high medical costs, and has a significant impact on the social economy; particularly, the loss of working hours brings a huge medical and economic burden to society [2]. The number of years of disability caused by LBP is estimated to have increased by 54% globally from 1990 to 2015, thus becoming the leading cause of global disability [3]. In March 2018, Lancet published three consecutive reports calling for prompt measures to be taken against the global LBP problem [3‐5]. In 2002, the International Labor Organization (ILO) explicitly added musculoskeletal diseases to the International List of Occupational Diseases (recommendation No. 194). Musculoskeletal diseases were further refined in the latest version of the list of occupational diseases approved by the ILO in 2010 [6]. Moreover, LBP has a high incidence in China, causing great harm and severe economic losses. The disease burden report of China and provincial administrative regions from 1990 to 2016 [7] ranked LBP as the first disease causing the loss of life years caused by disability from 2005 to 2016. Therefore, LBP is a global public health problem that needs urgent solution.

Therefore, this study explored the incidence and distribution characteristics of LBP by conducting a large-sample epidemiological investigation and study of key industries in different regions of China, and providing a reference for reducing global public health problems caused by LBP incidence.

This study investigated the epidemiological characteristics of LBP among occupational populations in key industries in China from January 2018 to December 2020, which is the largest population survey on LBP in China so far. It was found that LBP incidence in key industries or workers in China was 16.4%, which was slightly higher than that reported in other studies. According to the 2010 Global LBP disease burden study report [10], the global LBP incidence was estimated to be 9.4%, with the highest in Western Europe (15.0%), followed by North Africa/Middle East (14.8%), and Central and Latin America (6.6%).

This study found that LBP incidence in greenhouse vegetable farmers was higher than that in other industries. Field investigations have shown that greenhouse planting is a challenging task. Greenhouse vegetable farmers work in greenhouses for at least three-quarters of a year. Owing to the greenhouse’s narrow working space, farmers are predominantly in a bad working posture, such as large forward tilt and bending of the back, and kneeling or squatting for a long time. In addition, owing to the low degree of mechanization of greenhouse operations, there are almost no power tools and auxiliary tools to use, resulting in more repetitive operations and heavy physical labor of greenhouse vegetable farmers. These operational characteristics increase the risk of LBP among greenhouse vegetable farmers. It is worth mentioning that the medical personnel in this survey were also found to have high LBP incidence. An increasing number of domestic and international reports have shown that the incidence rate of WMSDs among medical staff is generally high. This finding is consistent with the results of this study. A survey on WMSDs of dentists in Western countries from 2005 to 2017 showed that the incidence of WMSDs was between 10.8–97.9% and the prevalence in most studies was more than 60% [11], which is higher than the survey results of this study. This may be related to the LBP determination method used in this study. The NIOSH judgment method was adopted in this study. The four judgment criteria are stricter than those of the Nordic Questionnaire [8]. Therefore, the prevalence in this survey was slightly lower than that reported in other surveys.

In terms of individual factors, results showed that age, BMI, smoking status, sports, and other factors are closely related to the occurrence of LBP. The incidence of WMSDs increased linearly with age under 45 years. The cumulative effect can explain this result; with increasing age, the musculoskeletal system of the body shows a trend of degradation. The longer the length of service, the longer the exposure to risk factors. Therefore, acute or chronic loads act on the musculoskeletal tissue, resulting in injury accumulation and increased musculoskeletal diseases [12]. After the age of 45, the incidence of WMSDs showed a downward trend. The field survey found that the management of many enterprises will adjust the operation positions of front-line workers according to the age of workers; that is, front-line workers will be adjusted to auxiliary positions with a light load or promoted to management positions such as team leaders. This may also explain the decline in the incidence of WMSDs. This survey found that the risk of LBP increased with increasing BMI. Houda Ben et al. [13] also found that BMI > 25 kg / m² was closely related to LBP occurrence. Dianat et al. [14] have also found that light BMI is a protective factor for LBP. Further, the survey found that occasional smoking and occasional or regular physical exercise were protective factors against LBP. This finding is consistent with the results of previous studies. Regular smoking aggravates LBP. Abdugad et al. [15] found that smoking is a risk factor for LBP. Smoking causes intervertebral disc degeneration by interfering with intervertebral disc metabolism, proteoglycan, and collagen synthesis, which may lead to LBP [16]. Previous studies have shown that [13, 17], a weekly regular physical activity can reduce LBP risk. According to the American Physical Therapy Association guidelines [18], moderate- to high-intensity exercises are recommended for LBP without pain, and low-intensity exercises for LBP with generalized pain. Research shows that [19] moderate physical exercise can enhance muscle strength and endurance, improve cardiovascular function, promote the diffusion of tissue fluid, ensure the absorption of nutrition by bone and muscle tissue, and alleviate muscle fatigue. Therefore, appropriate physical exercise may reduce the risk of LBP.

In terms of workplace factors, adverse posture operation, frequent repetitive movements as the trunk, working in the same posture at a high pace, bending slightly with the trunk, bending heavily with the trunk, frequently turning around with the trunk, and lifting heavy loads are risk factors for LBP, while often standing at work is a protective factor. Moreover, previous studies have shown that [20], stretching/overstretching and repeated bending at work may be risk factors for LBP. Studies have shown that [21] workers who need to repetitively bend at work are 97% more likely to develop LBP than those who do not.

Research shows that [22], long-term continuous poor posture while working can easily cause blood circulation disorder, serious insufficient blood supply in the spine area, and the inability of the muscles and bones to absorb nutrition, which can easily cause muscle tissue ligament strain. LBP can occur when there is a continuous low-load or short-term strong-load impact. Laboratory research shows that [23, 24], there is a positive correlation between heavy physical load and physical exertion. Coenen et al. [25] found that handling more than 25 kg per day could cause the annual incidence rate of LBP to increase by 4.3%.

In terms of psychosocial factors, this study shows that staff shortages and doing the same job almost daily can increase the risk of LBP, and abundant resting time and deciding the rest time independently can reduce the occurrence of LBP, which is consistent with previous research results. Research shows that [26] psychosocial factors play an important role in the development of LBP. High job requirements are closely related to the occurrence of LBP. Frequently working overtime, a fast work pace, and insufficient time to complete work can lead to WMSDs [27]. According to the 2010 National Health Interview Survey [28], female workers work 41–45 hours a week, and male workers work more than 60 hours a week, increasing the risk of LBP. Therefore, ensuring adequate rest time can relax muscle tissue, reduce the pressure on the lumbar intervertebral disc, and prevent the occurrence of LBP. This study shows that autonomous work progress control is a protective factor against LBP. Domestic and international scholars have reported similar results. Werner et al. [29]. found that a lower perceived decision authority (i.e., lack of rules, decision-making, and participation) is related to wrist WMSDs. If workers can decide the pace of their activities, theoretically, they can avoid activities that aggravate their symptoms and thereby allow healing to occur.

In summary, the incidence of LBP among occupational groups in key industries in China was slightly higher than that reported in other countries and regions. The risk factors that may lead to LBP mainly include individual factors, such as age, BMI,

smoking status, and sports; workplace factors, such as poor posture while working and lifting heavy loads; and psychosocial factors, that is, staff shortages and monotonous repetitive work almost daily. Because of this, when making the global public health strategy for prevention, treatment, management, and research of LBP, decision makers and employers should consider the individual, workplace, and psychosocial factors mentioned above to make comprehensive ergonomic preventions and interventions.