Prevalence of low back pain and associated risk factors amongst adult patients presenting to a Nigerian family practice clinic, a hospital-based study

Abstract Background Low back pain (LBP) is a common health problem with concomitant disability which has assumed a public health importance in our setting. Objectives The aim of this study was to determine the prevalence of LBP and associated risk factors amongst adult patients attending the General Outpatients’ Clinic of the University College Hospital in Ibadan, Nigeria. Method This was a cross-sectional study of 485 respondents. A semi-structured questionnaire was used to obtain information on socio-demography, lifestyle, occupation and other risk factors associated with LBP. Results There were 288 (59.4%) female and 197 (40.6%) male respondents. The point prevalence of LBP was 46.8%. Occupational activities, previous back injury and tobacco smoking were significant associated factors for the total population. For the female respondents, logistic regression analysis showed that a waist circumference of 88 cm or more, dysmenorrhea, previous back injury and being engaged in an occupation were the most significant factors associated with LBP. However, previous back injury was the most significant factor associated with LBP for the male respondents. Conclusion The prevalence of LBP amongst adult patients in our setting is high, with preventable and treatable predisposing factors. Public health efforts should be directed at educating people on occupational activities and lifestyle habits.


Introduction
Musculoskeletal problems are prevalent amongst the adult population. 1 Globally, chronic low back pain (LBP) is a common health problem. 2 People with chronic LBP experience huge social, mental, physical and occupational disruptions. 3 The mental impact of LBP include anxiety, depression and sleeplessness, whilst poor physical performance and deterioration in health status are the physical impacts. 1 LBP results in an inability to carry out social activities and it decreases the capability to perform occupational activities since it mostly affects adults of working age. 1,4 Disability caused by LBP stems from the pain and/or loss of function inflicted on the sufferers. Chronic LBP is one of the four disabilities causing musculoskeletal conditions -the others being osteoarthritis, osteoporosis and rheumatoid arthritis. 5 The economic burden of LBP on the society, especially in lowresourced continents like Africa, is enormous and continues to increase. Billions of dollars spent annually on managing LBP further constrains the fragile health care system in Africa, which is already ravaged by the HIV epidemic. 5 About 40% of sick absences from work is because of LBPmaking it the second most common cause of workplace absenteeism after the common cold. 6 Chronic LBP is the most common musculoskeletal problem encountered in the workplace, with attendant loss of quality of life and financial difficulty. 7 Chronic LBP is prevalent in many industrialised societies with prevalence rates of 21% and 39% being reported in the general population -and even higher in the occupational setting. 8 In the USA, LBP is the commonest musculoskeletal illness with 12% -30% of the population affected at any given time. 9 Occupation-related factors are the most important risks associated with LBP. 9 More than 80% of the population will experience an episode of LBP at some time during their lives. 10 The clinical course is benign for most, with 95% of those afflicted recovering within a few months of onset. Some, however, will not recover and will develop chronic LBP, i.e. pain that lasts for three months or longer. 10 Risk factors for developing LBP could be immutable (nonmodifiable) or mutable (modifiable). The immutable factors are age, parity, previous history of LBP and major scoliosis, whilst the mutable factors include a sedentary lifestyle, obesity, tobacco smoking and drug dependence. 11 Other mutable factors are occupation-related: poor posturing, prolonged sitting, twisting, bending, stooping and lifting of heavy loads. 11 There is scanty information available on LBP in resourceconstrained countries like Nigeria. 7 This may be due to fact that LBP is perceived to be of little public health importance when compared with other medical conditions such as hypertension and diabetes mellitus. 7 This study was carried out to determine the point prevalence and risk factors of LBP amongst adult patients presenting to a family practice clinic in Nigeria.

Ethical consideration
The head of the Family Medicine department (UCH, Ibadan) approved this study. Respondents gave their informed consent before the administration of their questionnaire and physical examination.

Context of the study
The study was conducted at the General Outpatients' (GOP) Clinic of the Family Medicine Department of the University College Hospital (UCH) in Ibadan, Nigeria. UCH is a tertiary institution founded in 1957 in the cosmopolitan city of Ibadan. Ibadan is the capital of the Oyo state in south-western Nigeria and has a population of 3.6 million people, mainly of the Yoruba tribe. 12 Most patients coming to UCH are seen first at the GOP Clinic, which functions as a secondary care clinic within a tertiary hospital setting. Patients are at first contact seen by consultants and resident doctors in family medicine.

Design
This was a cross-sectional study.

Study population
The population consisted of 485 patients who presented to the GOP Clinic (UCH) between 15 January 2011 and 30 March 2011. The inclusion criteria were all patients aged 18 years and above who consented to take part in the study. Those who did not consent to the study, who had congenital deformity of the spine or who were too ill to participate in the study were excluded.

Sampling technique
All adult patients who met the study criteria were consecutively selected.

Procedure
A semi-structured questionnaire was used to interview the respondents. The questionnaire was pretested to determine if the questions were clear and comprehensive enough to address the set objectives of the study and necessary amendments were then made. Information obtained from the respondents included their socio-demographic characteristics and lifestyle habits. Additionally, their health care utilisation pattern was obtained by asking them about the number of times they had been hospitalised for LBP, the total period spent on admission, the frequency of outpatient hospital visits in the last year and the treatment they sought for their LBP. Anthropometric measurements of height, weight, waist and hip circumferences were carried out for all respondents.
The weight (in kilogram) was divided by the height (meter) and then squared to calculate the body mass index (BMI). The BMI was graded along the World Health Organization's (WHO) classification, where 'Underweight' refers to a BMI less than 18.5 kg/m 2 , 'Normal' to a BMI of 18.5 kg/ m 2 -24.9 kg/m 2 , 'Overweight' to a BMI of 25.0 kg/m 2 -29.9 kg/m 2 and 'Obese' to a BMI greater than 30.0 kg/m 2 . To identify individuals with possible health risks, the waist circumference of the respondents was measured and this was based on the threshold values of ≥ 88 cm for women and ≥ 102 cm for men. 14 The waist/hip ratio (WHR) was calculated by dividing the waist circumference by the hip circumference. 14 The cut-off point of WHR was defined as ≥ 0.85 for women and ≥ 1.00 for men. 14 The questionnaire took an average of 22 min to be completed.

Anthropometric measurements
Height was recorded to the nearest 0.1 m with a measurement stand (stadiometre) that was positioned on a flat surface. The respondents were asked to remove their shoes and their heels were positioned against the wall, with their scapula, buttocks and heels resting against the wall. Female respondents were asked to remove their headwear. The weight of the respondents was measured to the nearest 0.1 kg using a standard weighing scale manufactured by Hana, China. Respondents stood on the weighing scale after removing their personal effects. The researcher made the readings whilst standing in front of the respondents and the zero mark was checked for accuracy after every reading. Waist and hip circumferences were measured to the nearest 0.1 m using a flexible non-elastic measuring tape.

Follow-up
Respondents were treated for their primary health complaints and those needing further treatment were referred to other specialty clinics within the facility.

Analysis
Administered questionnaires were checked, sorted and coded serially at the end of each study day. The data was entered, cleansed and analysed using SPSS® (version 16). Descriptive statistics was employed for the socio-demography, lifestyle and health care utilisation pattern of the respondents.
Categorical and discrete variables were tested using the Chisquare statistics and continuous variables were tested using the t-test. The relationship between socio-demography, lifestyle, health care utilisation and LBP was explored using logistic regression analysis. The p-value of significance was set at < 0.05.

Results
There were 288 (59.4%) female and 197 (40.6%) male respondents in the study population, with the female to male ratio being 1.5 to 1. The mean ± standard deviation (SD) of the respondents' age was 42.5 ± 15.5 years (range: 18 to 85 years). Their monthly income ranged from 2000 to 400 000 Naira ($13.33 to $2666.67) with a median income of 18 500 Naira ($123.33). The modal age group was less than 30 years and only 70 respondents (14.4%) were elderly. The majority of the respondents were married and 306 (63.1%) were literate, having completed the first 10 years of formal education (i.e. attained senior secondary and tertiary education). There were 331 respondents (68.2%) living with their immediate family (spouse and children or grandchildren) and 363 (74.8%) were currently engaged in occupational activities. The male respondents were mostly self-supporting whereas the females were mostly dependent on their spouses for financial support ( Table 1). The self-reported point prevalence of LBP was 46.8% ( Figure 1). Table 2 shows the socio-demographic characteristics of the respondents by the prevalence of LBP. The point prevalence of LBP was higher amongst men compared with women (50.3% vs. 44.4%), but without statistical significance (χ 2 = 1.586, p = 0.208). The prevalence of LBP increased gradually with age: from 44.9% for respondents younger than 30 years to 55.6% for the age group 51 years -60 years. However, a reduction in the prevalence of LBP was observed after the age of 60 ( Figure 2). There was therefore no statistical association between the prevalence of LBP and age (χ 2 = 3.007, p = 0.558). A higher prevalence of LBP was found in respondents who only had primary school education (55.7%), lived alone (50.6%), had more than five children (52.3%) and were selfsupporting (49.6%), as shown in Table 2. The prevalence of LBP was significantly higher amongst respondents who were currently engaged in occupational activities than those who were not (49.9% vs. 37.7%), where χ 2 = 5.421 and p = 0.020 ( Table 2). The majority (80%) of the respondents in social class I had LBP. However, Table 2 shows that there was no significant association between social class and LBP (χ 2 = 4.185, p = 0.382).
The highest proportion of LBP (63.6%) was found amongst respondents who commonly adopted the stooping position during their daily activities, whilst the lowest proportion (48.5%) was found in those who commonly adopted the standing position (Table 3). There was no significant association between commonly adopted posture and LBP (χ 2 = 2.174, p = 0.704). The prevalence of LBP was significantly higher amongst respondents who had previous back injury (91.3%) compared with those who did not (44.8%), where χ 2 = 14.64 and p < 0.001. The lifestyle habits of the respondents showed that 71 respondents (14.6%) regularly consumed alcohol, 12 respondents (2.5%) smoked tobacco and 102 respondents (21.0%) engaged in regular physical exercise. The prevalence of LBP was significantly higher in respondents who smoked tobacco than those who did not (91.7% vs. 45.7%), where χ 2 = 9.946 and p = 0.002. However, no association was found between the prevalence of LBP and alcohol consumption or physical exercise. Mattress or foam (94.8%) was the commonest sleeping material used by the respondents, with the majority (83.7%) using the soft type. The majority of respondents using either the firm type (55.4%) or the orthopedic type (70.0%) had LBP. However, there was no significant association between the sleeping material and LBP (χ 2 = 1.950, p = 0.377). Amongst the female respondents, the prevalence of LBP was significantly higher in those who had dysmenorrhea compared with those who did not (57.9% vs. 39.6%), where χ 2 = 7.565 and p = 0.006 (Table 3).
Anthropometric measurements of the respondents showed that the mean weight of the respondents was 66.7 kg ± 13.8 kg (37 kg -129 kg) and the mean height was 1. where t = 83.340 and p < 0.0001. Conversely, the mean BMI of the female respondents was significantly higher than those of their male counterparts (25.91 ± 5.52 vs. 24.16 ± 5.29), where t = 11.758 and p = 0.001. The mean waist circumference of the respondents was 79.2 cm ± 12.9 cm (50 cm -128 cm) and the mean hip circumference was 87.2 cm ± 15.4 cm (43 cm -133.1 cm). The mean waist/hip ratio (WHR) was 0.91 ± 0.07 (0.48 -1.36). The mean waist and hip circumference of the female respondents was significantly higher than those of their male counterparts (81.11 ± 13.79 vs. 76.37 ± 10.89, where t = 16.001 and p < 0.0001, and 89.82 ± 16.10 vs. 83.29 ± 13.45, where t = 21.473, p < 0.0001) respectively. However, the mean WHR of the females was significantly lower than those of the males (0.908 ± 0.07 vs. 0.923 ± 0.08), where t = 5.267 and p = 0.022 (Table 4). Table 5 depicts the physical characteristics of the respondents by the prevalence of LBP. The majority of the respondents (45.2%) had a normal BMI, whilst 46.8% were either overweight or obese. The highest proportion of LBP (48.6%) was found in those who were overweight, but there was no significant association between LBP and BMI (χ 2 = 0.739, p = 0.864). A higher proportion of men (70%) with a  waist circumference of 102 cm or more reported LBP than those with a waist circumference less than 102 cm (49.2%). However, this difference was not statistically significant (χ 2 = 1.643, p = 0.200). Amongst the females, the prevalence of LBP was significantly higher in those with a waist circumference of 88 cm or more than in those whose waist circumference was less than 88 cm ( (Table 5).

Discussion
There is a global burden of LBP. The prevalence amongst Africans is also rising and it is a cause for concern. 5 The prevalence of LBP in this study was found to be 46.8%. This is similar to the point prevalence of LBP amongst rice farmers in Thailand, a developing country. 15 It is also comparable to the prevalence of 46% in a study amongst staff in a rural hospital in Nigeria, 8 but it is higher than the point prevalence of 20% from a study amongst office workers.
The prevalence of LBP in this study was higher amongst men compared with women. In a review by Punnett, the attributable factor for LBP was also higher amongst men (41%) than women (32%). 2 The reason proffered was that men usually engage in occupations associated with heavy physical workload and whole-body-vibration compared with women. 2 This higher prevalence in males was corroborated by another group of researchers. 7 In contrast to the findings in our study, female rice farmers in Thailand were more likely to develop LBP than males. 15 Another study amongst staff in a rural hospital also found that female workers had a greater prevalence of LBP. 8 Some authors reported that the risk of developing LBP increases with advancing age and amongst females, however, others studies reported no such association between these factors. 16 Louw reported in a systematic review that the point prevalence of LBP amongst African adolescents and adults was 12% and 32% respectively. 5 Similarly, Taechasubamorn et al. reported the highest prevalence of LBP amongst young adults aged 25 years to 34 years. 15 Older people were found to experience the more persistent and severe form of LBP compared with young adults. 17 A report from Sweden showed that LBP was common amongst elderly Post Office pensioners who had previously engaged in lifting heavy loads for more than 20 years. 17 In this study, occupational activities and previous back injury were significantly associated with LBP. Thirty-seven percent of back pain worldwide accounts for an estimated 0.8 million disability-adjusted life years (DALY) with resultant work time and economic loss. 18 Physical efforts, such as manual exertion and exposure to whole-body-vibration are the common physical ergonomics related to LBP. 9 Some authors found that the majority of those reporting LBP were frequently exposed to 'stressful situations' in their occupation. 11 The highest proportion of LBP in this study was found amongst respondents who commonly adopted the stooping position during their daily activities. This is comparable to the findings of another Nigerian study that associated LBP with heavy physical work, bending, poor posture and prolonged sitting or standing. 8 In addition, most rice farmers experienced increased LBP from slouched sitting (56.2%), forward bending (70.8%) and lifting (83.2%). 15 The majority (57.3%) of the respondents using either the firm or orthopedic mattresses had LBP. Our study found no significant association between LBP and the sleeping materials (p = 0.377). This result differed from the multicenter trial by Kovacs, where pain and disability amongst patients with chronic, non-specific LBP improved when using the medium firm mattresses. 19 The firmness of the mattress was rated in their study along the European Committee for Standardization scale, with the firmest mattress rated as 1 and the softest rated as 10. 19 Self-assessment of the mattress type was carried out by the respondents in this study, which could have affected the results.
Tobacco smoking was significantly associated with LBP amongst the respondents. This was in agreement with previous studies in which the prevalence of LBP was higher amongst current smokers and ex-smokers than in nonsmokers, 8 as well as the study by Vindigni that reported higher levels of smoking in people with LBP. 11 For the female respondents in this study, logistic regression analysis showed that a waist circumference of 88 cm or more (p = 0.005, OR = 1.029, CI = 1.009 -1.050) was significantly associated with LBP. This is similar to the report in which 71% of the respondents were found to be either overweight or obese, with 16% not being physically active and 35.9% engaging in less than 30 minutes of exercise daily. 11 Being overweight is more common in women compared with men. Its prevalence increases in mid-life and then decreases over time. Being overweight causes an increase in the pressure on the structures of the lower back and that may lead to lumbar disc herniation and subsequent LBP. Studies reported an association between being overweight and experiencing LBP. 7,20 Chronic medical illnesses, such as hypertension, diabetes mellitus and obesity with advancing age, have been reported to influence the occurrence of tendon and ligament diseases which can lead to LBP. 21 For the female respondents, logistic regression analysis showed that dysmenorrhea (p = 0.012, OR = 2.260, CI = 1.197 -4.268) was associated with LBP. This is similar to the study in which LBP and headaches were found to contribute the most to the severity of dysmenorrhoea. 22

Conclusion
Back pain is a common cause of absenteeism at work and functional disability, which has assumed a public health importance. 23 In Australia, LBP is commonly treated with exercise. 11 Lifestyle modification, such as regular exercise, smoking cessation and weight reduction, and culturally acceptable health promotion programmes have been found to be beneficial in reducing the disability associated with LBP. 5,11 Workers at risk of LBP need to modify their postures during occupational activities by preventing excessive flexion and extension movements. 2 In our setting there is a high prevalence of LBP amongst adult patients, with several modifiable risk factors identified. Various levels of prevention should be employed to alter occupational activities and lifestyle habits.