Prevalence and Associated Factors of Musculoskeletal Disorders (MSDs) among Greenhouse Workers

1. INTRODUCTION

MSDs are among the most common occupational diseases and leading causes of absenteeism, significantly reducing productivity [1, 2]. These disorders account for a major portion of occupational illnesses in work environments [3], resulting from damage to muscles, tendons, ligaments, joints, nerves, blood vessels, and soft tissues [4, 5]. MSDs represent one of the most prevalent work-related health issues worldwide, accounting for approximately 32% of all occupational diseases, according to 2014 data from the U.S. Bureau of Labor Statistics [6]. More recent statistics from the U.S. Department of Labor indicate that MSDs result in 1.6 cases of injury, illness, or fatality per 100 full-time workers [7]. MSDs account for 7% of all societal diseases, 14% of physician visits, and 19% of hospitalizations, with 62% of affected individuals experiencing movement restrictions, according to the International Institute's report. The American Occupational Health and Safety Organization ranks MSDs as the second most significant work-related disease in terms of frequency, severity, and progression potential [3]. In Iran, these disorders rank fourth for total disability [1], with Tehran's Social Security Organization Medical Commission reporting that 14.4% of disability-causing diseases are MSD-related [8]. Research indicates that MSDs cause over half of workplace absenteeism cases [9, 10], with back pain being the most prevalent manifestation affecting 50-90% of adults [2, 9-11].

The prevalence of these musculoskeletal discomforts leads to reduced work capacity and quality, increased medical costs, greater work time loss, and premature disability among workers [10, 12].

Chronic spinal pain leads to distressing psychological effects and serious complications, including limited mobility, disability, job changes, and the overuse of oral and injectable medications for treatment [13,14]. Despite advances in workplace automation, many jobs still involve physical tasks such as manual material handling and tool use, which place biomechanical stress on the body [15, 16]. These physical demands often result in pain and discomfort across multiple body regions. Both ergonomics and industrial psychology highlight the significance of workload-induced stress, which can lead to physiological changes (e.g., increased heart rate), psychosocial effects (e.g., irritability), and behavioral outcomes (e.g., increased error rates) [17-19]. Excessive work pressure and poor posture, primary contributors to MSDs, remain central issues in workload-related investigations.

A study by Mostaghati et al. examining MSD prevalence and risk factors among agricultural machinery factory workers found MSD occurrence at 3.40%, with body-specific prevalence rates of 12.8% for back pain, 7.8% for knees, 6% for the neck, and 5% for shoulders [9]. The prevention of work-related MSDs has now become a national priority in many countries [18, 19]. Postural analysis serves as a powerful ergonomic assessment tool for work activities, where evaluating ergonomic risks associated with improper posture helps identify potential work-related MSDs [15, 20, 21]. The high prevalence across different body regions underscores the need for targeted ergonomic interventions in industrial settings. Agriculture represents one of the most physically demanding occupations, involving unavoidable risk factors for MSDs, such as heavy lifting, equipment handling, and sustained awkward postures, which contribute to conditions like osteoarthritis [22-24].

As one of the most prevalent occupational diseases, MSDs significantly reduce productivity, increase absenteeism, and may lead to permanent worker disability. Greenhouse workers are particularly vulnerable due to exposure to multiple ergonomic hazards, including repetitive motions, prolonged static postures, substantial weight-bearing, and insufficient recovery periods. The nature of greenhouse work, requiring frequent bending, kneeling, and transporting heavy loads in confined, humid environments, creates unique biomechanical stresses that elevate MSD risk. While previous research has documented MSD prevalence in general agricultural settings, greenhouse workers remain understudied despite facing compounded physical strain from microclimatic conditions. This study addresses this critical gap by investigating MSD patterns among greenhouse workers in Jiroft, a region known for intensive greenhouse farming. Our research aims to assess workers' health status and identify associated risk factors, responding to the urgent need for data on this high-risk occupational group. The findings will inform targeted interventions to protect this essential but vulnerable agricultural workforce.

2. METHODS AND MATERIALS

This cross-sectional study investigated 293 greenhouse workers in Jiroft city during 2023 using cluster sampling methodology. The sample size was determined through Morgan's table for a population of 1,200 workers, achieving a 95% confidence level with a ±5% margin of error. Researchers identified 12 major greenhouse complexes across Jiroft and randomly selected 5 geographically representative clusters. Within each selected complex, all eligible available workers were enrolled until reaching the predetermined sample size, ensuring broad operational representation while maintaining practical implementation. The sampling framework specifically targeted population size (N)=1,200, sample size (n)=293, confidence level=95%, and margin of error=±5%. This methodological approach balanced statistical rigor with fieldwork feasibility while capturing diverse greenhouse working conditions across the region. The study included participants who met the following criteria: agriculture must be their primary occupation, they must be capable of participating in the study, have no history of musculoskeletal diseases, be aged 18 years or older, and provide informed consent. On the other hand, individuals who were non-professional or temporary workers, or those who provided incomplete questionnaire responses, were excluded from the study.

Data collection utilized a validated two-part questionnaire combining demographic characteristics with the Nordic Musculoskeletal Questionnaire (NMQ). The demographic section considered age, work experience, anthropometric measures (height/weight), and musculoskeletal history. The NMQ assessed symptoms across nine anatomical regions (neck, shoulders, upper/lower back, elbows, hands/wrists, thighs, knees, ankles, and feet). Previous Iranian validation studies confirmed the questionnaire's face validity, with excellent reliability metrics: standard error of measurement (SEM=0.56-1.76), intraclass correlation coefficients (ICC>0.70), and Kappa agreement coefficients (0.78-1.00) [25].

Data collection was carried out using two methods: literate workers self-completed the questionnaires, while illiterate participants had their responses recorded by researchers through interviews. After data collection, the analysis was conducted using SPSS-24 software, applying both descriptive and inferential statistical techniques. Descriptive analysis included measures of central tendency (mean), dispersion (standard deviation), range, and frequency distributions. For inferential analysis, Pearson correlation, independent t-tests, and ANOVA were employed to explore relationships between musculoskeletal disorders (MSDs) and demographic/work variables, such as gender, age, height, and work history. All statistical tests applied a significance threshold of p≤0.05. This dual analytical approach enabled a comprehensive examination of both population characteristics and significant associations between risk factors and musculoskeletal outcomes.

3. RESULTS

The study population consisted of 293 greenhouse workers, with 261 (89.1%) male and 32 (10.9%) female participants. MSDs showed a striking gender disparity, affecting 89.3% of male workers compared to 10.7% of female workers. The majority of participants (over 50%) were aged 20-40 years, with a mean body mass index of 22.8 ± 3.82. Demographic characteristics revealed that 215 workers (73.4%) resided in rural areas, 118 (40.3%) were married, and 117 (39.9%) were single. Educational attainment was limited, with 126 workers (43%) being illiterate and 112 (38.2%) having only a high school diploma or less. Economically, 160 workers (54.6%) earned ≤10 million tomans monthly. Lifestyle factors showed concerning patterns: 172 workers (58.7%) reported no leisure-time physical activities, and 265 (90.4%) did not engage in regular sports. Only 220 workers (75.1%) had no underlying medical conditions. Statistical analysis identified two significant risk factors for MSDs: increasing age (p<0.05) and physical inactivity (p<0.05). Strikingly, sedentary workers had a 6.72-fold greater risk of developing MSDs compared to their physically active counterparts (95% CI: 2.27-19.9). These findings highlight the vulnerable demographic profile and modifiable risk factors among greenhouse workers that contribute to their high MSD burden. (Table 1)

The study revealed that 149 out of 293 workers (50.9%) were affected by musculoskeletal disorders (MSDs). Analysis of the affected body regions indicated that 76 individuals (25.9%) experienced discomfort in a single region, while 40 individuals (13.7%) reported pain in two or three regions simultaneously. Additionally, 22 workers (7.5%) had discomfort in all examined body areas. These results highlight the high prevalence of MSDs among greenhouse workers and indicate varying severity levels, with a notable proportion experiencing multi-region symptoms (Table 2).

The 12-month prevalence analysis revealed significant variation in MSD distribution across anatomical regions. Lower back disorders emerged as the most prevalent condition (36.2%, n=106), followed by shoulder pain (19.5%, n=57) and knee pain (17.1%, n=50). Ankle problems represented the least frequent complaint (7.5%, n=22). These findings demonstrate a clear hierarchy of musculoskeletal vulnerability among greenhouse workers, with the lumbar spine bearing the greatest occupational burden. The complete anatomical distribution of work-related musculoskeletal complaints is detailed in Table 3.

Statistical analysis demonstrated significant relationships between MSD prevalence and specific risk factors. Chi-square tests identified strong associations with both age groups (p=0.014) and physical activity levels (p<0.001). Physically inactive workers showed a markedly increased risk, with 6.72 times greater odds of developing MSDs compared to their active counterparts (95% CI: 2.27-19.9). Notably, the study found no statistically significant associations between MSDs and sex, body mass index, or work duration (all p>0.05) (Table 4).

4. DISCUSSION

MSDs represent one of the most significant occupational health challenges in agricultural settings, with substantial impacts on workforce productivity. This study highlights the particularly high prevalence of MSDs among greenhouse workers, revealing several critical risk factors. The elevated MSD rates stem primarily from occupational exposures, including repetitive motions, forceful exertions, sustained awkward postures, mechanical stresses, and work-related fatigue [26, 27]. Three key modifiable factors emerge as major contributors: (1) insufficient ergonomic training during worker education [23, 24], (2) prolonged static postures without adequate recovery periods [23, 26], and (3) biomechanically stressful movements causing asymmetric muscle loading and uneven pressure distribution, particularly during bending and twisting tasks [23, 24, 26]. These risk factors disproportionately affect the neck, back, and spinal regions, explaining the observed anatomical distribution of disorders. The findings align with broader occupational health literature documenting similar MSD patterns across diverse worker populations [8, 28-30]. These results underscore the urgent need for targeted ergonomic interventions in greenhouse environments, including comprehensive worker training programs, implementation of microbreaks, and modification of high-risk work techniques. Such evidence-based measures could substantially reduce the musculoskeletal burden in this vulnerable occupational group while maintaining agricultural productivity.

The results of this study indicate that the majority of greenhouse workers were male, with a higher prevalence of MSDs observed among male workers compared to female workers, which can be attributed to several factors, including differences in work activities, physical capacity, and training levels. Male workers typically perform more physically demanding tasks, such as heavy lifting, machinery operation, and equipment handling, which place greater strain on the musculoskeletal system and increase the risk of disorders. While men generally have greater physical capacity for heavy labor, repeated exposure to strenuous tasks contributes to their higher MSD prevalence [23, 31, 32]. Gender differences in training approaches may also play a role, as male workers often receive less ergonomic guidance due to assumptions about their physical capabilities, potentially perpetuating unsafe work practices and further elevating their MSD risk. These findings are consistent with previous research linking physically demanding roles to increased MSD incidence [23, 31], though cultural factors, such as the potential underreporting of symptoms by male workers, may also influence the observed prevalence rates. Male workers often perceive physical labor as an inherent job requirement, resulting in inadequate training on proper work techniques and injury prevention. This lack of training may contribute to their higher rates of MSDs. These findings are consistent with research by Punnett et al. [31] and Lorusso et al. [32], who similarly observed higher MSD prevalence among male workers. However, contrasting studies by Bruce and Bernard, as well as Rahimabadi et al. [1, 33], reported a greater prevalence of MSDs among female workers. These discrepancies may arise from variations in sample sizes, specific workgroups studied, or cultural and social contexts. Women may be more inclined to report symptoms due to social factors, whereas men might underreport pain due to job security concerns or workplace perceptions.

The study findings revealed that among greenhouse workers, 25.9% (76 workers) experienced MSDs in one body region, likely due to prolonged static postures without sufficient rest. Meanwhile, 13.7% (40 workers) exhibited disorders in two or three regions, potentially caused by uncoordinated muscle contractions and uneven spinal pressure distribution. The 7.5% (22 workers) with whole-body MSDs may have developed these widespread disorders as a result of insufficient ergonomic training, improper work methods, continuous heavy labor, and inadequate recovery time [23, 24]. These patterns align with previous research, which demonstrates variable MSD distributions among agricultural workers, with most cases involving single-region disorders, while fewer workers develop multi-region or systemic musculoskeletal problems [30, 34-36].

The study findings demonstrated that greenhouse workers experienced the highest prevalence of MSDs in the back (36.2%), followed by the shoulders (19.5%) and knees (17.1%), reflecting the particular vulnerability of these body regions during agricultural work. These anatomical areas endure substantial biomechanical stress during both light and heavy work activities in greenhouse environments [2, 9]. The development of MSDs in these regions stems from prolonged static postures without adequate rest periods, leading to uncoordinated muscle contractions and uneven pressure distribution across spinal structures. These results align with previous research by Asghari et al. [4], who similarly identified the lumbar region, back, knees, and shoulders as the most commonly affected areas. The observed pattern further corresponds with findings from the studies of Mostaghaci et al. [9], Choobineh et al. [37], and Ismail et al. [38], confirming the consistent distribution of MSDs among workers performing similar occupational tasks.

The study found a significant association between physical activity and MSD prevalence among greenhouse workers, suggesting that regular exercise may serve as a protective factor against MSDs. Properly planned sports activities can enhance muscle strength, improve flexibility, and promote more balanced pressure distribution across the body, thereby reducing MSD risk. These benefits likely explain the lower MSD rates observed among physically active workers. The protective effect of exercise aligns with previous findings by Nasl Saraji et al. [39] and Rahimabadi et al. [1], who similarly reported reduced MSD prevalence among workers engaged in regular physical activity, supporting the current study's conclusion about the musculoskeletal benefits of exercise for this occupational group.

CONCLUSION

In conclusion, the findings highlight a pronounced gender disparity in MSD prevalence, with male workers showing significantly higher susceptibility. This pattern may be attributed to gendered divisions of labor that often involve more strenuous physical tasks. Younger and middle-aged workers were also found to be more vulnerable to MSDs. The back, shoulders, and knees emerged as the most affected anatomical regions, reflecting the biomechanical stresses inherent in greenhouse work, such as prolonged static postures, repetitive motions, and heavy lifting. Notably, the observed association between regular physical activity and reduced MSD risk suggests that musculoskeletal health in this workforce may be modifiable through targeted interventions. The high prevalence of MSDs across multiple body regions underscores systemic occupational safety deficiencies. To address these findings, health policymakers should prioritize implementing comprehensive ergonomic training programs tailored specifically for greenhouse workers and management, while developing a systematic surveillance program to monitor their musculoskeletal health periodically.

LIMITATIONS OF THE STUDY

This study had several limitations. First, some potential participants declined to participate due to personal concerns, including fears about future job security. Second, the research was limited to greenhouse workers in southern Iran, which may affect the generalizability of the findings. Third, the cross-sectional design makes it difficult to establish causal relationships. To address these limitations, future studies should include larger sample sizes across multiple regions and employ longitudinal designs to enhance reliability. Additionally, using appropriate analytical methods to control for confounding factors would strengthen future findings.

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