Is obesity a risk factor for low back pain ? An example of using the evidence to answer a clinical question Background Obesity as a causal factor for low back pain has been controversial with no definitive answer to this date . The objective of this study was to determine whether obesity is associated with low back pain . In addition this paper aims to provide a step-by-step guide for chiropractors and osteopaths on how to ask and answer a clinical question using the literature . Introduction Obesity is a problem of epidemic proportion -LSB- 1,2 -RSB- . Despite record rates of non-physician supervised dieting and the availability of numerous weight loss programs , the problem is not abating -LSB- 3 -RSB- . Complicating this , is that most primary care physicians do not treat obesity , citing a lack of time , resources , insurance reimbursement , and knowledge of effective interventions as significant barriers -LSB- 4 -RSB- . Musculoskeletal disorders including low back pain -LRB- LBP -RRB- represent a considerable public health problem and a common diagnosis creating absenteeism and the need for disability pensions -LSB- 5 -RSB- . It is estimated that about 80 % of the United States and Canadian population will experience LBP during adulthood -LSB- 6 -RSB- . Most low back pain is self-limiting and will ultimately resolve in two weeks -LRB- 50 % of those affected -RRB- to six weeks -LRB- 90 % of those affected -RRB- , however it remains an intriguing clinical problem -LSB- 6 -RSB- . It is widely noted that the economic cost of obesity and its related disorders are staggering , with lifestyle related conditions such as diabetes mellitus and coronary heart disease placing a large economic burden on the health care system -LSB- 1-4 -RSB- . However , low back pain also has a significant socioeconomic impact . Cost estimates range from US$ 20 billion to $ 50 billion annually , with 10 % of the patients accounting for 85 to 90 % of the costs -LSB- 6 -RSB- . In Australia , Walker et al estimated the cost of low back pain in 2001 alone to be AUD$ 9.17 billion -LSB- 7 -RSB- . One question , which arises from the discussion concerning obesity , is whether obesity is a risk factor for low back pain . `` Buckwalter et al contended that a number of medical conditions including obesity , along with diabetes and hypertension , may influence the pathophysiology of diseases of the tendons and ligaments during the process of aging thus potentially leading to low back pain -LSB- 8 -RSB- . Along with low back pain , the conventional wisdom is that overweight persons are at risk of osteoarthritis in weight-bearing joints such as the knee , the hips , and feet -LSB- 9 -RSB- . To date , literature reviews have given conflicting views based on the available data and method of data retrieval . The purpose of this review is to establish , from recent research , if there is a causal link between obesity and the affliction of low back pain . A secondary purpose of this review is to present the concepts of evidence-based practice to aid the chiropractor or osteopath in looking for health-related evidence for their patients who present with obesity . Methods A MEDLINE search , from the National Library of Medicine , was used to ascertain pertinent articles between the years 1990 and 2004 . The use of keywords `` obesity '' , `` body mass index '' , `` BMI '' and `` low back pain '' was used to obtain relevant studies . The references of papers retrieved were also reviewed , as were key texts and references . This section is devoted to presenting the concepts of evidence-based practice -LRB- EBP -RRB- to demonstrate to the reader the discovery process for finding a possible link between obesity and low back pain . The EBP method used is shown in Table 1 . Table 1 Steps to asking the answerable question using EBP principles Step 1 : Asking an answerable question Step 2 : Selecting an evidence resource Step 3 : Executing the search strategy Step 4 : Examining the evidence summary Step 5 : Application of the evidence The first step in this process is `` asking an answerable question . '' In this paper we assume a patient has asked whether being overweight can cause low back pain . Construction of an appropriate answerable question would possibly be `` Does an increased BMI cause low back pain ? '' `` Does being overweight create osteoarthritis ? '' In this way questions can be constructed to allow the practitioner to effectively answer a clinical concern . Once the answerable question has been constructed the next task is to find an adequate resource . Internet access to the U.S. National Library of Medicine 's MEDLINE or PUBMED , these database systems are considered by many experts to be the most up to date data source on medically related topics . The next step is to determine keywords to place in the search engine . From the answerable question -LRB- s -RRB- it can be appreciated that the initial keywords will be `` low back pain '' , `` BMI '' and `` osteoarthritis . '' This search constitutes the third step . In initiating the search , one should look for the search engines `` limits '' area . In this area can one designate an age group -LRB- ex : 45 to 60 years -RRB- , date span of the literature search , -LRB- ex : 1998 to 2003 -RRB- , and to select either English language or articles in foreign languages . Once the search has been completed , the articles , which may answer the question , are isolated and can be read . Step four involves collating the evidence to answer the question . In searches one may find answers that were not known to exist , and information that may challenge an already preconceived notion . The evidence summary should list the main author and year the paper was published . This is in order to retrieve the data should anyone wish to examine the source . As an example of an evidence summary see Table 2 . Table 2 Recent evidence : Obesity and low back pain -LRB- chronological order -RRB- Author , Year -LRB- Ref -RRB- N BMI LBP Association Melissas , 2003 -LSB- 14 -RSB- 50 > 40 58 % direct Bener , 2003 -LSB- 10 -RSB- 802 -LRB- 26.4 males / 27.8 females -RRB- 56.1 % males 73.8 % females moderate Tsuritani , 2002 -LSB- 16 -RSB- 709 -- 40.3 % none Bowerman , 2001 -LSB- 4 -RSB- 252 -- 29.2 % none Kostova , 2001 -LSB- 12 -RSB- 898 -- -- increased risk Bayramoglu , 2001 -LSB- 15 -RSB- 25 -- -- direct Mortimer , 2001 -LSB- 13 -RSB- 475 30 -LRB- 43.6 % -RRB- 31 -- 40 -LRB- 28.8 % -RRB- 40 + -LRB- 1.3 % -RRB- -- increased risk Han , 1997 -LSB- 11 -RSB- 7018 women 5887 men NR -- females increased risk N = number ; BMI = body mass index ; LBP = low back pain ; NR = not reported It is at this time that the clinician is ready for the final step of applying the evidence . In our example clinical data from the experimental literature may or may not indicate that there is a link between overweight and low back pain . Results The literature search into obesity and joint pain revealed several studies pertinent to the debate . Table 2 reveals an overview of the studies selected . Several studies -LSB- 4,10-13 -RSB- had large populations to draw from yet the data from these studies were not in agreement as to a cause or association . In fact , only two studies -LSB- 14,15 -RSB- found a direct association for obesity as a risk factor while two -LSB- 4,16 -RSB- studies found no association . Several of the studies reviewed were unable to clarify BMI to the satisfaction of the authors . Discussion Interest in the association between obesity and low back pain has piqued researchers interest for many years . Intuitively , a burgeoning waistline and an increased lordotic lumbar spine led researchers to conclude that overweight people would be more prone to low back pain . Historically , Kellgren and Lawrence -LRB- 1958 -RRB- found that that the prevalence of disk degeneration with obesity was not significant -LSB- 17 -RSB- . However , it was not until the mid-1970 's when several studies observed a possible association . Obesity was found to increase the prevalence of disk degeneration significantly in a study by Magora and Schwartz in 1976 -LSB- 18 -RSB- . Barton et al -LRB- 1976 -RRB- , in a review of 144 cases , found that 70 % of those who complained of low back pain had been classified as being overweight -LSB- 19 -RSB- . This basic research appeared to conclude what was already intuitively thought about low back pain and increased weight . Body mass index Before an in-depth discussion of low back pain and obesity can ensue , the concept of Body Mass Index -LRB- BMI -RRB- needs to be discussed . BMI is a measure of fatness and is calculated by dividing the patient 's weight in kilograms by height in metres squared kg/M2 -LSB- 20 -RSB- . It is widely accepted , easily measured , and predicts morbidity and mortality in many populations -LSB- 15 -RSB- . Obesity is generally defined as a BMI of 30 kg/m2 and higher -LSB- 20,21 -RSB- . Overweight is defined as a BMI between 25 and 30 kg/m2 -LSB- 19,20 -RSB- . Overweight tends to be more common in men with obesity being more prevalent among women -LSB- 21 -RSB- . When body weight is increased 20 % above average , mortality rises to 20 % for men and 10 % for women -LSB- 22 -RSB- . -LRB- Table 3 -RRB- Overweight individuals demand more from their cardio-respiratory and musculoskeletal systems -LSB- 22 -RSB- . It is known that more than 50 % of adult Americans have a BMI equal to or greater than 25 -LSB- 23 -RSB- . Although there are certain limitations to BMI i.e. large muscular athletes who are in good cardiovascular shape , the rationale behind these numbers is that , across large population groups , there is an increased prevalence of certain diseases in people with a BMI over 25 , and a much greater risk of disease and death in those with a BMI over 30 -LSB- 4 -RSB- . Being overweight or obese substantially raises the risk of developing hypertension , coronary heart disease , type 2 diabetes , stroke , gallbladder disease , sleep apnea and other respiratory problems , prostate and colon cancers -LSB- 4,23 -RSB- . Yet , the evidence to date linking it to low back pain is not as clear cut as it is with the previously stated pathologies . Table 3 Clinically relevant differentiation between obesity and overweight Overweight Obesity BMI of 25.0 to 29.9 kg/m2 BMI greater than 30 kg/m2 BMI calculation without benefit of BMI charts Body Mass Index -LRB- BMI -RRB- charts and hand held scales are available for individual clinician use . It is , however , unknown to what degree chiropractors or osteopaths use such tools . The following section is designed to aid the clinician with calculating BMI without benefit of chart or hand held scales . As noted earlier , BMI is calculated as weight in kilograms divided by height in square metres -LSB- 20,24 -RSB- . This method is often too difficult to calculate for most people . A simpler method for those using the imperial system of measures is to take body weight in pounds × 703/height in inches squared . For example , a person weighing 150 pounds at 6 foot tall would correspond to a BMI of 20.3 . TABLE 4 Table 4 Calculation of BMI 150 × 703 = 105450 divided by 72 inches -LRB- 6 foot -RRB- squared . 105450 divided by 5184 -LRB- 72 × 72 -RRB- = 20.3 BMI . Additional research findings Leboeuf-Yde concluded from a review of the literature that due to lack of evidence , body weight should be considered a possible weak risk indicator and suggested that there is insufficient data to assess if it is a true cause of LBP -LSB- 25 -RSB- . Kostova found that in men over 40 , overweight , obesity and number of pack years of smoking , estimated by duration of smoking and daily cigarette consumption -LRB- more than 20 years and more than 20 cigarettes per day -RRB- , increased the risk of developing back disorders -LSB- 12 -RSB- . Despite these two studies , Garzillo et al and Leboeuf-Yde et al have given conflicting opinions -LSB- 26,27 -RSB- . Garzillo 's review of the data revealed a possible association between obesity and low back pain only in the upper quintile of obesity , and no evidence of a temporal relationship between weight change and changes in low back pain -LSB- 26 -RSB- . Leboeuf-Yde concluded from a twin study that obesity is modestly positively associated with low back pain , in particular with chronic or recurrent low back pain -LSB- 27 -RSB- . What appears to be a main concern in linking obesity as a causal factor for low back pain is the numerous variables encountered in these subjects . For example , it is hypothesized that overweight adult females may have negative self-concepts and body images compounded by chronic low back pain and obesity , these may be confounding factors -LSB- 28 -RSB- . Other variables such as less activity and/or muscular weakness leading to obesity are also possible considerations . Obesity and low back pain-related conditions Not only is there controversy in obesity and low back pain , but there exists conflicting views of obesity and low back pain-related conditions such as spondylosis , decreased physical activities and discal herniation . The studies demonstrating a positive association are many . O'Neil et al noted that increasing BMI is associated with more frequent findings of osteophytes -LRB- bone spurs -RRB- at both the thoracic and lumbar spines -LSB- 29 -RSB- . The correlation of osteophytes and increased BMI is highest at the thoracic level -LSB- 29 -RSB- . Biering-Strenson et al noted absolute weight and BMI are significantly higher in persons 60 years of age with spondylosis -LSB- 30 -RSB- . Both men and women with BMI of 30 kg/m2 or higher were twice as likely to have difficulties in performing a range of basic daily physical activities -LSB- 30 -RSB- . Compared with women with BMI lower than 25 kg/m2 , those with BMI of 30 kg/m2 or higher were 1.5 times more likely to have symptoms of intervertebral disk herniation -LSB- 31 -RSB- . Conversely , Luoma et al concluded that disc degeneration is not related to body height , overweight , smoking , or the frequency of physical activity -LSB- 32 -RSB- . In addition , studies by Riihimaki , Symmons , and Kang have shown no association between BMI and low back related problems -LSB- 33-35 -RSB- . Confounding the data is that the mechanism by which excess body weight causes osteoarthritis is poorly understood -LSB- 9 -RSB- . It is believed that contributions from both local increased force across the joint and systemic factors play a role -LSB- 9 -RSB- . A discriminating factor between fit and unfit patients with back pain may be the fact that fit persons more frequently are still employed , and as such may be involved more in physical activity -LSB- 36 -RSB- . Table 5 indicates where the research currently exists for the link between low back pain and obesity along with obesity and osteoarthritis . Table 5 BMI-related risk of osteoarthritis and low back pain If your BMI is then your risk based solely on BMI < 25 minimal 25 -- < 27 minimal 27 -- < 30 minimal 30 -- < 35 moderate 35 -- < 40 moderate > 40 moderate to high We conclude , based on the available evidence to date , that those individuals with a BMI of under 30 are at a minimal risk of developing low back pain while those persons whose BMI increases to over 30 are a moderate risk of developing low back pain . We also suggest , based on the findings of the Melissas study -LSB- 14 -RSB- of those patients who relieved their low back pain symptoms after obesity surgery , that patients with a BMI of greater than 40 are at a high risk of developing low back pain . Albeit controversial , Table 5 may lead to a further refinement of risk of osteoarthritis and low back pain based solely on BMI . Limitations of obesity as a risk factor for low back pain A significant difficulty in ascertaining cause and effect between obesity and low back pain is undoubtedly the term `` low back pain '' itself . Low back pain is a symptom not a diagnosis . A specific diagnosis , instead of the generalized form of `` low back pain '' may help separate out the association between LBP and obesity . The Agency for Health Care Policy and Research -LRB- AHCPR -RRB- in their 1995 Acute Low Back Problems in Adults noted common diagnoses used to explain back problems -LSB- 37 -RSB- -LRB- Table 6 -RRB- . Given these possible diagnoses one can readily appreciate the dilemma in attempting to link obesity with its specificity in measurement to a broad symptom such as low back pain . Table 6 Common diagnoses used to explain back symptoms Annular tear Adult spondylolysis Myofascitis Fibromyalgia Disc syndrome Strain Spondylosis Lumbar disc disease Facet syndrome Degenerative joint disease Sprain Spinal OA Disc derangement/disruption Dislocation * Other potential causes of low back pain symptomology Failed Back Surgery Syndrome * Osteoporosis * Urinary tract infection * Compression fracture * Somato-visceral mimicry syndrome * Organic pathology -LRB- tumor , rheumatoid , endometriosis , arthritic disorders -RRB- * Leg length inequity * Sacro-iliac dysfunction * Hip disorder * ** Disagreement in research as cause of low back symptomology Morbid obesity ? ** OA = osteoarthritis Another problem is the hypothesis that a person who suffers with continuing bouts of low back pain may be predisposed , due to inactivity or inability to exercise , to gain weight thus increasing their BMI . This hypothesis to our knowledge , has yet to be fully discussed and investigated . Conclusion The data for a link between obesity and low back pain appears to be controversial . Yet , this does not adequately address the appropriate therapeutic approach to the obese patient with low back pain . The studies chosen for this review fail to document a definitive causal link between obesity and low back pain . Further research and epidemiologic data is needed to continue the search for a definitive answer . Competing interests The author -LRB- s -RRB- declare that they have no competing interests .

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low back pain
obesity
association
risk factor