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ISSN : 1598-7248 (Print)
ISSN : 2234-6473 (Online)
Industrial Engineering & Management Systems Vol.18 No.4 pp.630-637
DOI : https://doi.org/10.7232/iems.2019.18.4.630

Prevalence of Work-Related Musculoskeletal Disorders among Thai Oil Palm Workers in Khao Phanom District, Krabi Province, Thailand

Sirothorn Tewtow, Petcharatana Bhuanantanondh*, Keerin Mekhora
Faculty of Physical Therapy, Mahidol University, Nakhon Pathom, Thailand
Corresponding Author, E-mail: petcharatana.bhu@mahidol.edu
May 7, 2019 September 27, 2019 October 18, 2019

ABSTRACT


Thailand is one of the top three palm oil producers in the world. Krabi province has the largest oil palm plantation area in Thailand. Oil palm agriculture is one of the main occupations of people in Krabi province. Harvesting oil palm is labor intensive. Therefore, it can adversely affect the quality of life and increase the risk of developing work-related musculoskeletal disorders (WMSDs) among oil palm workers. However, in Thailand, research on the prevalence of WMSDs among oil palm workers is still limited. Thus, this study aimed to survey the prevalence of WMSDs among oil palm workers in Khao Phanom district, Krabi province, Thailand. A cross-sectional study was conducted among 125 oil palm workers who worked in Khao Phanom district, Krabi province, Thailand during harvesting stage. A questionnaire used in this study consisted of questions regarding individual factors, work-related factors, psychosocial factors, and WMSDs by using modified Nordic questionnaire. All data were conducted by face-to-face interview. The results of this study showed that the prevalence of WMSDs among oil palm workers during the past 12 months was 98.4%. The highest prevalence of WMSDs during the past 12 months was reported in the lower back (75.2%) followed by shoulder (52.8%) and neck (44.0%). Furthermore, the prevalence of WMSDs during the past 7 days was 64.8%. The highest prevalence of WMSDs during the past 7 days was reported in the lower back (32.0%) followed by shoulder (20.0%) and elbow (12.8%). In conclusion, the prevalence of WMSDs among Thai oil palm workers was high. Therefore, further study is warranted to provide more information that may help to develop guideline for preventing WMSDs among Thai oil palm workers.



초록


    1. INTRODUCTION

    Thailand is one of the top three palm oil producers in the world. These top three countries, which are Indonesia, Malaysia, and Thailand, are all located in Southeast Asia. The major palm oil exporters in the world are Indonesia and Malaysia (Department of Agricultural Extension, 2016). In 2016, it was reported that Thailand exported palm oil for the amount of 117.25 million kilograms which produced 4.59 billion baht (Department of Agricultural Extension, 2017a). In 2017, it was reported that there were 4.75 million rais of oil palm plantation area in Thailand and the majorities of them are located in many provinces in the southern region of Thailand. Krabi is one of the top three provinces with regard to oil palm plantation areas and planters in Thailand (Department of Agricultural Extension, 2017b).

    Hazards and injuries are common in agricultural works (Nawi et al., 2016). It was reported that oil palm workers have the risk of getting work-related musculoskeletal disorders (WMSDs) (Nawik et al., 2015). WMSDs are characterized as musculoskeletal disorders related to workplace and work conditions (Armstrong et al., 1993). WMSDs can be caused by various sources and occur over a period of several days, weeks, months or even years from repetitive movements while working. Awkward working postures, forceful exertion, static muscular force, prolonged posture vibration, and contact stress (Sanders, 2004) can generate micro-trauma, and wear and tear on the body tissues and structures that can cause WMSDs (Stack et al., 2016). Thus, oil palm workers who have WMSDs can lead to many problems such as disability, decreased work performance, and increased medical cost (Ng et al., 2014a;Mokhtar et al., 2013).

    The process of oil palm harvesting includes harvesting fresh fruit bunches (FFB), collecting loose fruits, transporting the FFB and loose fruits to the collection point as well as loading the FFB into the lorry. The characteristics of oil palm harvesting tasks demand oil palm workers to be associated with very intensive work. For example, oil palm harvesting tasks involve lifting and carrying the heavy FFB on the shoulder during transporting the FFB to the collection point (Deros et al., 2016), and being in awkward postures during cutting the FFB and collecting the loose fruits. These risks will lead to the increased prevalence rate of WMSDs (Mokhtar et al., 2013;Syazwani et al., 2016). A study by Ng et al. (2015) described the prevalence rate of WMSDs of oil palm harvesters from 10 oil palm plantation zones that located in the southern region of Peninsular, Malaysia. They reported that 86% of the participants suffered WMSDs during the past 12 months. However, the total prevalence rate of WMSDs during the past 7 days was 45%, which was lower than the total prevalence rate of the past 12 months.

    Although oil palm workers have high risk of getting WMSDs, there are very limited information about the prevalence of WMSDs among this group of workers in Thailand. Thus, the current study aimed to survey the prevalence of WMSDs and to examine risk factors associated with the highest 12-month prevalence of WMSDs among oil palm workers in Khao Phanom district, Krabi Province, Thailand.

    2. MATERIAL AND METHODS

    This study was a cross-sectional study conducted among oil palm workers who worked in Khao Phanom district, Krabi province, Thailand during harvesting stage. The oil palm workers were recruited by approaching through the oil palm harvesting manager to provide information of this study. All participants read and signed an informed consent prior to the data collection. The inclusion criteria were Thai oil palm workers aged between 18 and 60 years old and having at least 1 year experience in oil palm harvesting. Participants who had an accident, severe trauma in the past that caused current musculoskeletal disorders and neurological disorders were excluded. This study was approved by the Mahidol University Central Institutional Review Board (MU-CIRB COA. NO. 2017/154.2808).

    2.1 Questionnaire

    All data in this study were conducted by face-to-face interviews. The questionnaire consisted of questions regarding individual factors (i.e., age, gender, body mass index (BMI), marital status, education level, work status, income, underlying disease, smoking status and drinking alcohol status), work-related factors (i.e., types of harvesting tasks, working landscape, number of working areas, number of working hours/day, weight of FFB and weight of loose fruits), psychosocial factors, and musculoskeletal symptoms in nine body parts (i.e. neck, shoulder, elbow, wrist/hand, upper back, lower back, hip/thigh, knee, and ankle/foot) during the past 12 months and the past 7 days by using the modified Nordic musculoskeletal questionnaire (Kuorinka et al., 1987).

    2.2 Data Analysis

    Statistical data analysis was performed by Statistical Packages for the Social Science (SPSS) software for Windows version19. Descriptive statistics were used to analyze for mean, standard deviation, frequency and percentage of individual factors, work-related factors, psychosocial factors, and musculoskeletal symptoms during the past 12 months and 7 days. Chi-square test was used to determine the association between individual factors, work-related factors, psychosocial factors, and low back pain. Any variables with a p-value < 0.1 from the chisquare test were included in the multivariate logistic regression analysis. A p-value < 0.05 were considered as significant.

    3. RESULTS

    3.1 Individual Factors

    A total of 125 oil palm workers participated in this study. Table 1 shows characteristics of all participants. Participants consisted of 82 males (65.6%) and 43 females (34.4%) with the mean age of 38.45 ± 11.59 years. The mean body mass index (BMI) of the participants was 22.98 ± 3.30 kg/m2. The majority of the participants were married (90.4%) and had the highest education at primary school level (66.4 %). Moreover, 88.8% of the participants were employees and the mean income were 12,400 ± 5,600.62 baht/month. Most of the participants had no underlying diseases (83.2%). Of the 125 participants, 49.6% and 54.4% were smokers and drinkers, respectively.

    3.2 Work-Related Factors

    Regarding work-related factors, the mean oil palm harvesting experience of the participants was 10.56 ± 8.38 years. The majority of them had less than or equal to 10 years of experience (67.2%) and worked in plain and slope landscape (92%). In this study, oil palm harvesting tasks was categorized into three main tasks which were FFB cutter, FFB collectors and loaders, and loose fruit collectors. Of the 125 participants, 52 participants (41.6%) were FFB cutters, 30 participants (24.0%) were FFB collectors and loaders, and 43 participants (34.4%) were loose fruit collectors (Table 2). Table 3 presents the number of working area and duration of work for each oil palm harvesting task, and the weight of FFB and loose fruit per container.

    3.3 Psychosocial Factors

    The results showed that the majority of the participants strongly agreed to the following statements: “If you have problems, you can always talk with your family” (83.2%), “Your work is not safe” (49.6%) and “Your work environment makes you feel discomfort” (55.2%). The majority of the participants moderately agreed to the following statements: “You like your work” (48%), “Income is enough for living expense” (58.4%) and “Always feel that you have to work under time pressure” (30.4%). The majority of the participants disagreed to the following statements: “Always feel that your work is monotonous” (60.8%) and “Often have to force yourself to work, even when you feel tired” (32%). Table 4 shows the level of agreement for each statement regarding psychosocial factors.

    3.4 Prevalence of WMSDs of All Participants

    The prevalence of WMSDs in nine body parts during the past 12 months of all participants was 98.4%. The top three 12-month prevalence of WMSDs among oil palm workers were in the lower back (75.2%), shoulder (52.8%) and neck (44.0%). In addition, the prevalence of WMSDs during the past 7 days was 64.8%. The top three 7-day prevalence of WMSDs were in the lower back (32.0%), shoulder (20.0%) and elbow (12.8%) (Table 5).

    3.5 Prevalence of WMSDs in the FFB Cutters Group

    The prevalence of WMSDs in nine body parts during the past 12 months of FFB cutters was 96.2%. The top three 12-month prevalence of WMSDs among FFB cutters were in the lower back (71.2%), neck (63.5%), and shoulder (59.6%). In addition, the prevalence of WMSDs among FFB cutters at any body parts during the past 7 days was 71.2%. The top three 7-day prevalence of WMSDs were in the lower back (25.0%), shoulder (23.1%) and elbow (17.3%) (Table 6).

    3.6 Prevalence of WMSDs in the FFB Collectors and Loaders Group

    The prevalence of WMSDs in nine body parts during the past 12 months of FFB collectors and loaders was 100%. The top three 12-month prevalence of WMSDs among FFB collectors and loaders were in the shoulder (70.0%), lower back (63.3%) and elbow (60.0%). In addition, the prevalence of WMSDs among FFB collectors and loaders during the past 7 days was 63.3%. The top three 7-day prevalence of WMSDs were in the lower back (33.3%), shoulder (26.7%) and elbow (16.7%) (Table 7).

    3.7 Prevalence of WMSDs in the Loose Fruit Collectors Group

    The prevalence of WMSDs in nine body parts during the past 12 months of loose fruit collectors was 100.0%. The top three 12-month prevalence of WMSDs among loose fruit collectors were in the lower back (88.4%), knee (60.5%) and hip/thigh (46.5%). In addition, the prevalence of WMSDs among loose fruit collectors during the past 7 days was 58.1%. The top three 7-day prevalence of WMSDs were in the lower back (39.5%), shoulder, hip/thigh and knee (11.6%) as well as neck and ankle/ foot (7.0%) (Table 8).

    3.8 Factors Associated with the Highest 12-Month Prevalence of WMSDs

    The highest prevalence of WMSDs during the past 12 months among oil palm workers was at the lower back. Table 9 shows factors associated with low back pain during the past 12 months among oil palm workers. From chisquare test, the results revealed that gender, drinking, and time pressure were the factors that showed a p-value < 0.1. Therefore, these factors were selected for further analysis. The results from multiple logistic regression analysis showed that gender and time pressure were significantly associated with low back pain. Females had 7.689 times greater risk of having low back pain than males (adjusted OR = 7.689 [95% CI, 1.156-51.155; p = 0.035]). Furthermore, participants who moderately - strongly agreed to the statement: “Always feel that you have to work under time pressure” was 2.981 times more likely to have low back pain than those who disagree-agree a little to the statement (adjusted OR = 2.981 [95% CI, 1.111-7.995; p = 0.030]).

    4. DISCUSSION

    This study aimed to survey the prevalence of WMSDs among oil palm workers in Khao Phanom district, Krabi Province, Thailand. The findings revealed that the prevalence of overall WMSDs among oil palm workers during the past 12 months and 7 days were 98.4% and 64.8% respectively. The high prevalence of WMSDs among oil palm workers might be because the workers exposed with many ergonomics hazards (e.g., awkward postures, repetitive work, and lifting heavy FFB). The results of this study showed that the prevalence of WMSDs during the past 12 months and 7 days among oil palm workers were higher than in previous studies (Henry et al., 2015;Ng et al., 2014a;Ng et al., 2015). A study by Ng et al. (2014a) reported that the prevalence of WMSDs among oil palm workers in Malaysia within the past 12 months and the past 7 days was 93% and 43.4%, respectively. A more recent study by Ng et al. (2015) found that the prevalence of WMSDs within the past 12 months was 86% and within the past 7 days was 45%. Another study by Henry et al. (2015) also reported that the prevalence of WMSDs during the past 12 months among oil palm workers was 58.3%. The higher prevalence in this study compared to previous studies (Henry et al., 2015;Ng et al., 2014a;Ng et al., 2015) might be due to the differences in oil palm harvesting stage and harvesting methods.

    Moreover, the findings of this study showed that the highest prevalence of WMSDs among oil palm workers during the past 12 months was in the lower back, followed by shoulder and neck. These findings were in agreement with the results reported by Henry et al. (2015). The results of this study found that low back pain was the highest complaint during the past 12 months which was consistent with the results from previous studies (Henry et al., 2015;Mohd et al., 2005;Ng et al., 2014a;Ng et al., 2015). Lower back, shoulder and neck pain were found to be common WMSDs during the past 12 months among oil palm workers (Henry et al., 2015;Ng et al., 2014a;Ng et al., 2015).

    In addition, this study found that the highest prevalence of WMSDs among oil palm workers during the past 7 days was in the lower back which was consistent with other studies (Ng et al., 2014a;Ng et al., 2015). The findings of this study showed that the shoulder and elbow were ranked second and third highest prevalence of WMSDs among oil palm workers. Likewise, a study by Ng et al. (2015) reported that the most common complaints of WMSDs were in the lower back (28%), shoulder (13%) and elbow (7%). Pain in the lower back, shoulder and elbow regions were found to be common WMSDs during the past 7 days among oil palm workers (Ng et al., 2014a;Ng et al., 2015).

    Furthermore, the current study reported that the total prevalence of WMSDs among the FFB cutters during the past 12 months was 96.2%. Previous study by Nawi et al. (2016) also reported high prevalence of WMSDs among the FFB cutters which was 100%. Moreover, the findings of the current study showed that the highest prevalence rate of WMSDs in the past 12 months were in the lower back, followed by neck, and shoulders, respectively. This finding was in agreement with a study by Nawi et al. (2016) which reported that the highest complaints of WMSDs were in the lower back (100%), followed by neck (97.0%), upper back (93.9%) and right shoulder (90.9%), respectively. The high prevalence of WMSDs among FFB cutters might be related to awkward working postures during FFB harvesting (Ng et al., 2014b).

    For the FFB collectors and loaders, this study found that the prevalence of WMSDs during the past 12 months was 100% which was the same with the prevalence of WMSDs reported in the previous study (Nawi et al., 2016). Moreover, the findings of the current study found that the top three highest prevalence rate of WMSDs in the past 12 months were in the shoulder, lower back, and elbow which were in agreement with the results reported by Nawi et al. 2016. In their study, they reported that the prevalence of WMSDs was highest in the shoulder (100%) and lower back (100%). The high prevalence of WMSDs among FFB collectors and loaders might be because the lifting process during collecting and loading FFB into the lorry involves several awkward postures such as twisting the body and repetitive movements with both hands above shoulder level while carrying and loading heavy FFB (Deros et al., 2016;Nawi et al., 2016). These working postures of lifting process during collecting and loading FFB were also consistent with the study by Ng et al. (2014b).

    For loose fruit collectors, in this study the total prevalence of WMSDs during the past 12 months was 100% which was the same with the prevalence of WMSDs previously reported by Nawi et al. (2016). In addition, the results of the current study showed that the top three highest prevalence of WMSDs during 12 months were found in the lower back, knee, and hip/thigh. These findings were in agreement with the results reported by Nawi et al. (2016). In their study, the prevalence of WMSDs was the highest in the lower back (100%), followed by calf (90.6%), knee (78.1%), and buttock (78.1%), respectively. This might be because working posture during loose fruit collecting process involves repetitive trunk bending, stooping, and squatting while sweeping or picking loose fruits.

    In addition, the findings of this study showed that gender was significantly associated with lower back pain. Female participants were 7.689 times more likely to have low back pain compare to males. This results were consistent with results from previous studies, which reported that the prevalence of WMSDs in females was higher than males (de Zwart et al., 1997;Erick and Smith, 2014). This might be because apart from work female workers also have to perform the household activities which might reduce their physical recovery from work. Also, in many cultures, it may be more acceptable for women to complain about discomfort than for men (Treaster and Burr, 2004).

    Moreover, there was also significant association between time pressure and low back pain among oil palm workers. Participants who agreed that they had to work under time pressure were 2.981 times more likely to have low back pain compare to those who disagree or agree a little. Research has shown that time pressure is one of the work-related stressors (van Vuuren et al., 2005;Elfering et al., 2002). A similar significant association between work-related stressor and low back pain was also reported by previous studies (Hartvigsen et al., 2004;Warming et al., 2009).

    There were several limitations of this study. First, this study was conducted among oil palm workers only in Khao Phanom district, Krabi province. Therefore, the findings cannot be implied to the general population of oil palm workers. Second, this study were conducted through face-to-face interviews, thus there might be recall bias. Third, there was no physical examination to confirm WMSDs reported by the workers.

    5. CONCLUSION

    The current study aimed to survey the prevalence of WMSDs among oil palm workers in Khao Phanom district, Krabi Province, Thailand. This study found that the prevalence of WMSDs among Thai oil palm workers was high. The highest prevalence of WMSDs among oil palm workers was in the lower back region. In addition, for the FFB cutters and loosed fruit collectors, the highest prevalence of WMSDs during the past 12 months was in the lower back. However, for the FFB collectors and loaders, the highest prevalence of WMSDs during the past 12 months was in the shoulder. Furthermore, gender and time pressure were significantly associated with low back pain among oil palm workers. Therefore, further study is warranted to provide more information that may help preventing WMSDs among Thai oil palm workers.

    ACKNOWLEDGEMENTS

    The authors would like to thank all oil palm workers who participated in this study.

    Figure

    Table

    Characteristics of all participants (n = 125)

    Work-related factors of all participants (n = 125)

    Number of working area and duration of work for each oil palm harvesting task, and the weight of FFB and loose fruit per container

    Level of agreement for each statement regarding psychosocial factors (n = 125)

    Prevalence of WMSDs among all oil palm workers (n = 125)

    Prevalence of WMSDs of FFB cutters (n=52)

    Prevalence of WMSDs of FFB collectors and loaders (n=30)

    Prevalence of WMSDs of loose fruit collectors (n=43)

    Unadjusted and adjusted odds ratio (OR) with 95% confidence interval (CI) of low back pain during the past 12 months

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