Computer Use and Carpal Tunnel Syndrome: A 1-Year Follow-up Study
Abstract and Figures
Computer use is increasingly common among many working populations, and concern exists about possible adverse effects of computer use, such as carpal tunnel syndrome (CTS).
To estimate the prevalence and incidence of possible CTS and to evaluate the contribution of use of mouse devices and keyboards to the risk of possible CTS.
A 1-year follow-up study with questionnaires conducted in 2000 and 2001 at 3500 workplaces in Denmark, followed on each of the 2 occasions by a clinical interview on symptom distribution and frequency.
The questionnaire was sent to 9480 members of a trade union, with an initial response rate of 73% (n = 6943), and 82% (n = 5658) at follow-up.
At baseline, there were 3 outcome measures: tingling/numbness in the right hand once a week or more as reported in the questionnaire; tingling, numbness, and pain in the median nerve in the right hand confirmed by clinical interview; and tingling, numbness, and pain in the median nerve in the right hand at night confirmed by clinical interview. At 1 year of follow-up the main outcome of interest was onset of symptoms among participants who had no or minor symptoms at baseline.
The overall self-reported prevalence of tingling/numbness in the right hand at baseline was 10.9%. The interview confirmed that prevalence of tingling/numbness in the median nerve was 4.8%, of which about one third, corresponding to a prevalence of 1.4%, experienced symptoms at night. Onset of new symptoms in the 1-year follow-up was 5.5%. In the cross-sectional comparisons and in the follow-up analyses, there was an association between use of a mouse device for more than 20 h/wk and risk of possible CTS but no statistically significant association with keyboard use.
The occurrence of possible CTS in the right hand was low. The study emphasizes that computer use does not pose a severe occupational hazard for developing symptoms of CTS.
Figures - uploaded by Johan Hviid Andersen
Author content
All figure content in this area was uploaded by Johan Hviid Andersen
Content may be subject to copyright.
... Many studies indicate that computer-operating workers run a higher risk of upper extremity musculoskeletal disorders, carpal tunnel syndrome (CTS) in particular (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). However, despite ample evidence, the association between work on computers and the development of CTS is still controversial, since the available data are inconclusive (19)(20)(21)(22)(23)(24)(25)(26)(27)(28). ...
... However, despite ample evidence, the association between work on computers and the development of CTS is still controversial, since the available data are inconclusive (19)(20)(21)(22)(23)(24)(25)(26)(27)(28). What seems to lack is an all-encompassing analysis of factors implicated in the development of CTS (3,(7)(8)(9)(10)(12)(13)(14)(15)(16)(17)(18). Apart from work-related long-term strain on the hands or wrists in awkward position, repetition, forceful hand/arm exertion, or vibration reported by a number of studies (29)(30)(31)(32)(33)(34), there are some non-occupational risks, such as genetics, female sex, age, obesity, diabetes, thyroid diseases, inflammatory arthritis, hand trauma, and pregnancy that can be involved in CTS development (35)(36)(37)(38)(39). ...
The contribution of certain occupational and personal factors to the development of carpal tunnel syndrome (CTS) is still uncertain. We investigated which specific occupational and non-occupational factors correlate with the level of clinical manifestations and work disability related to CTS. The study included 190 workers who work with a computer and have diagnosed CTS (100 men, 90 women, aged 20–65 years). Subjective experience of CTS-related impairments was assessed with the Symptom Severity Scale (SSS) and the Functional Status Scale (FSS) of the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ). The objective, neural impairments were tested with electrodiagnostics (EDX), whereas CTS-related work disability data were collected from medical records. We found a high inter-correlation between BCTQ, EDX, and work disability data. These also showed high correlations with certain occupational factors (duration of computer-working in months and hours spent daily in computer-working, certain ergonomic, microclimatic, and other occupational conditions) and non-occupational factors (demographic and lifestyle factors: nutritional status, diet, smoking, alcohol consumption, and physical activity). Despite its limitations, our study has identified occupational and non-occupational risk factors that can aggravate CTS and work disability, but which can also be improved with workplace and lifestyle preventive and corrective measures. More research is needed, though, to establish the possible causal relationships and the independent influence of each of those risk factors.
... In the United States, CTS carries an annual financial burden of approximately USD 2 billion [2]. CTS development has been associated with occupational exposures such as computer use in offices [3,4], repetitive work and high forces in industrial settings [5,6], and raw meat processing in poultry plants [7]. Chronic exposure to occupational risk factors, such as excessive force, repetitive exertions, and non-neutral postures have been linked to an increased risk for developing CTS [8]. ...
Background/Objectives: Mechanical compression of the median nerve is believed to be responsible for idiopathic carpal tunnel syndrome (CTS) due to fibrosis of the subsynovial connective tissue (SSCT). Vascular consequences have also been observed in structures of the carpal tunnel, raising speculation regarding the role of factors such as ischemia and edema in CTS pathology. Methods: We performed a mega-analysis from our database of over 10 years of studies. Mixed-effects models were used to address the disconnect between mechanical and vascular influences on CTS; the effects of biomechanical factors and CTS status were evaluated on carpal tunnel tissue mechanics and blood flow. Altered blood flow was also induced during tissue motion to draw inferences regarding the cyclical relationship between tissue mechanics and fluid flow changes on CTS pathology. Results: Greater movement speed and flexed wrist postures were found to contribute to greater shear strain. Flexed wrist postures and greater fingertip force were found to increase median nerve blood flow. Greater CTS severity was associated with lower median nerve blood flow. Finally, brachial blood flow restriction as a surrogate for elevated carpal tunnel pressure was found to alter tissue motion and increase carpal tunnel tissue shear strain. Conclusions: Finger movement speed, force application, wrist posture, and altered fluid flow in the carpal tunnel contribute to changes in outcomes associated with the development of CTS. The mechanistic findings from this paper should be incorporated into future research to update the damage model for CTS pathology.
... Health Concerns and Solutions for Computer Users. Extensive computer use, especially among developers, can lead to various health issues like Computer Vision Syndrome (CVS) [2] and Carpal Tunnel Syndrome [5]. To address physical strain, ergonomic tools like adjustable chairs and desks [10], along with regular breaks [14], are commonly recommended. ...
Long sessions of computer use introduce physical and mental health risks, particularly for programmers and intensive computer users. Breathing exercises can improve focus, reduce stress, and overall well-being. However, existing tools for such practices are often app-based, requiring users to leave their workspace. In this technical report, we introduce Nafas, a command-line interface (CLI) application designed specifically for computer users, enabling them to perform breathing exercises directly within the terminal. Nafas offers structured breathing programs with various levels tailored to the needs of busy developers and other intensive computer users.
... 84 The reported prevalence of CTS in the general population varies from 0.7% to 9.2% among women and from 0.4% to 2.1% among men. 85 A study on gamers found symptoms of CTS in over 60% of participants, with more than 50% reporting functional impairment. 86 A recent systematic review and meta-analysis by Mediouni et al investigated the potential association between CTS and computerrelated work. ...
The rapidly expanding realm of Electronic Sports (eSports) has captivated global attention, blurring the lines between virtual entertainment and traditional athletics. As participation in eSports continues to rise, these competitive gaming platforms are increasingly recognized as legitimate sports. However, with this surge in participation, there's a simultaneous increase in the susceptibility to health hazards, spanning both physical and psychological domains. Musculoskeletal injuries, caused by extended sedentary postures and repetitive motions, afflict eSports athletes, resulting in discomfort in the wrists and hands, alongside back and neck problems. The prolonged exposure to screens predisposes participants to vision-related concerns, highlighting the imperative of addressing ocular health within the eSports community. Simultaneously, the intense cognitive demands and competitive pressures exacerbate mental health challenges, resulting in depression and anxiety among players. Similar to traditional athletes, eSports competitors need appropriate protocols to minimize injury risks, alongside access to medical intervention to manage potential health hazards. This review comprehensively analyses the health dynamics of eSports, elucidating injury profiles, intervention strategies, and health optimization protocols essential for safeguarding the well-being of eSports athletes and enhancing awareness within the eSports community.
... Computer use has increased in workplaces and computers have become a necessary and indispensable part of almost all work environments [11,12]. Besides the positive effects of these technologies, the increase in computer use in workplaces and homes has also increased the prevalence of WRULDs [13][14][15]. The relationship between computer use duration and WRULDs has been shown in several studies, and the prevalence rates of musculoskeletal pain for 12 months were 55-69% for the neck and 15-52% for the upper limbs [16][17][18]. ...
Objectives. This study aimed to investigate the effects of academician's demographic characteristics and computer usage habits on upper limb musculoskeletal disorders (MSDs) and function. Methods. A cross-sectional observational study was conducted with 100 academicians. Data were collected using questionnaires, which included the patient-rated wrist evaluation questionnaire - Turkish version (PRWE-T), the Cornell musculoskeletal discomfort questionnaire - Turkish version (CMDQ-T), the upper extremity functional index - Turkish version (UEFI-T), demographic characteristics and average daily computer usage time. Results. A low-level significant correlation was found between the age of the individuals and the CMDQ-T forearm (p = 0.044; r = 0.202) and CMDQ-T wrist (p = 0.001; r = 0.337) scores. Women had higher CMDQ-T neck scores and lower UEFI-T scores than men (p < 0.05). Academicians who used computers for 6 h a day or more had higher PRWE-T and CMDQ-T neck, shoulder, upper arm and forearm scores, and had a lower UEFI-T score (p < 0.05). Conclusion. Neck, shoulder, upper arm and forearm symptoms were higher and upper extremity function was impaired in academicians who used computers for 6 h a day or more. Besides, gender and age were associated with upper limb MSDs and function, but occupation duration did not affect those outcomes in academicians.
... We identified 14 eligible publications for inclusion in this review on occupational physical and psychosocial exposures and the incidence of CTS that reported data from nine unique prospective cohort studies Dale et al., 2014Dale et al., , 2018Harris-Adamson et al., 2015Heilskov-Hansen et al., 2016;Lund et al., 2019;Roquelaure et al., 2020;Silverstein et al., 2010;Violante et al., 2016). Four of these publications (reporting data from three unique studies (Andersen et al., 2003;Nathan et al., 2005;Nathan et al., 2002;Werner et al., 2005) were also included in the previous review by van colleagues in 2009 (van Rijn et al., 2009b). Table 1 summarizes relevant characteristics of the study design and population of the included studies. ...
Context
Carpal tunnel syndrome (CTS) is caused by compression of the median nerve as it travels through the carpal tunnel into the wrist. It is the most common peripheral mononeuropathy and accounts for a large proportion of occupational upper extremity disorders. Teaching is an occupation associated with musculoskeletal disorders.
Aims
This study aimed to investigate the prevalence of CTS symptoms and related risk factors among schoolteachers in Al-Ahsa.
Settings and Design
A cross-sectional study was conducted on schoolteachers in Al-Ahsa, Saudi Arabia, during 2023.
Subjects and Methods
We distributed the Boston Carpal Tunnel Questionnaire to the teachers’ groups through social media in the form of an online questionnaire, and we visited schools to encourage participation.
Statistical Analysis Used
Data were analyzed using the Statistical Package for the Social Sciences. P < 0.05 was considered statistically significant.
Results
Our study included 619 schoolteachers. The syndrome symptoms were present in 71.1% of individuals, and functional disruption was present in 52.7%. The likelihood of exhibiting the symptoms is increased by being female, not participating in sports, having a chronic illness, writing for more than 4 h, and having symptoms in both hands.
Conclusions
We found a comparatively high percentage (71.1%) of the syndrome symptoms among schoolteachers working in Al-Ahsa, Saudi Arabia, which suggests that any signs of CTS in schoolteachers should be evaluated to ensure proper diagnosis and treatment.
Overuse of the mouse is one of the possible behaviors that trigger carpal tunnel syndrome (CTS). In this study, we designed Crimson Tendons, a mouse use behavior visualization system. The system consists of a physical visualization device and a data canvas that records mouse usage data. The physical device uses flowing red liquid to map the mouse usage state. We proposed a preliminary user test and performed qualitative and quantitative analyses. The experimental results indicated that the device was attractive to users. They would choose to take active breaks to watch the flowing effect of the device, and this feedback would help us iterate on the design concept. The system has a novel design and contributes to the promotion of office health by helping to improve people’s work habits and reduce the risk of CTS and other related diseases.
Introduction
The use of information devices like computers is skyrocketed in recent years, leading injuries. Carpal Tunnel Syndrome is a leading cause of upper extremity MSDs specially to banking workers. Hence, this paper was intended to highlight its magnitude associated factors in the study area.
Methods and materials
Institutional based cross-sectional study was conducted from September 13, 2021 to October 09, 2021. A total of 422 private and government owned computer user bankers were participated. Simple random sampling technique was used to select the study participants. Data were collected using Durkan’s compression test, flexion and compression test, Phalen’s test, and Tinel’s test. Multivariable logistic regression model was used to investigate the relationship between predictors and Carpal Tunnel Syndrome. P-value less than 0.05 was considered to declare as a significant and Adjusted Odds Ration for strength association between risk factors and Carpal Tunnel Syndrome.
Result
Among 422 participants, the annual prevalence of CTS was 11.7%. Being smoker [AOR: 4.2; 95% CI: 1.76–10.26], having > 5-year work experience [AOR: 7.98; 95% CI: 3.7-17.33], movement repetition [AOR: 3.9; 95% CI: 1.66–9.4] and lack of ergonomics training [AOR: 5.2; 95% CI: 2.8–9.5] were independently associated risk factors to Carpal Tunnel Syndrome.
Conclusion
Carpal Tunnel Syndrome was high (11.7%) among bankers in this study area. Carpal Tunnel Syndrome was predicted by smoking, length of employment, movement repetition, and not received ergonomics training. Therefore, fore the banking industry, it would be better to maintain strict follow-up and provision of ergonomics training.
Peripheral neuropathy is a general scientific term used to describe disorders of the peripheral nerves of any etiology. Along with postinfectious, diabetic, paraneoplastic, and alcoholic neuropathy, neuropathy of pregnancy represents one of the forms of this pathology. In this study, the authors conducted an analysis of domestic and foreign literature from open sources over the past 20 years. The study of available data revealed that the most common peripheral neuropathies observed during pregnancy are carpal tunnel syndrome, Bells palsy, and neuropathies affecting the lower extremities. Despite the paucity of information on peripheral neuropathy in pregnant women, its relevance is very high as it can significantly impair the quality of life during pregnancy and does not always disappear immediately after delivery, sometimes persisting for a certain period of time. The literature search was conducted in Scopus, Web of Science, PubMed, ScienceDirect, CyberLeninka, and RSCI databases using the following keywords: pregnancy; neuropathy; carpal tunnel syndrome; Bells palsy; review.
To study the prevalence of carpal tunnel syndrome (CTS) in the general population and the value of brachialgia paraesthetica nocturna (BPN) in diagnosing CTS, an age and sex stratified random sample of 715 subjects was taken from the population register of Maastricht (The Netherlands) and surrounding villages, between September 1983 and July 1985. The response rate was 70%. Of these, 12 CTS cases had already been diagnosed. Of the remaining subjects, 64 (13 men, 51 women) woke up because of BPN. Among these subjects 1 man and 23 women were found to have CTS. The prevalence rate of undetected CTS was 5.8% [95% confidence interval (CI): 3.5-8.1%] in adult women; 3.4 percent (95% CI: 1.5-5.3%) had already been diagnosed as CTS. The overall prevalence rate for men was 0.6% (95% CI 0.02-3.4%). These figures have to be regarded as minimal estimates. The overall diagnostic value of BPN for CTS was 38%, while for women only this was 45% (95% CI: 31-60%).
This investigation of current epidemiologic and ergonomic research demonstrates consistent relationships between certain computer-related factors and musculoskeletal disorders.
The published information about work-related carpal tunnel syndrome (CTS) was surveyed to identify risk estimates and possible biases influencing the risk estimates. Seventeen studies from the English-language literature were identified and study characteristics were coded for univariate and regression analysis. Country of publication, study population, force, and repetitive motion were significant predictors or risk, with R(2) = 0.57, adjusted R(2) = 0.43, Cp = 5.79, and AIC = 19.6 using the best-subset method of variable selection. Using the forward-variable selection method, country, study population, study type, and repetitive motion were significant predictors, with R(2) = 0.57, Cp = 6.24, p = 0.033. Excess risks of work-related CTS were consistent in the studies reviewed. Studies published in the United States reported higher risk estimates than did those published elsewhere. Some industrial populations were found to have higher risk estimates than others. Cross-sectional designs were the most common epidemiologic approach, but are not without methodologic concerns.
Carpal tunnel syndrome (CTS) is a cause of pain, numbness, and tingling in the hands and is an important cause of work disability. Although high prevalence rates of CTS in certain occupations have been reported, little is known about its prevalence in the general population.
To estimate the prevalence of CTS in a general population.
General health mail survey sent in February 1997, inquiring about symptoms of pain, numbness, and tingling in any part of the body, followed 2 months later by clinical examination and nerve conduction testing of responders reporting symptoms in the median nerve distribution in the hands, as well as of a sample of those not reporting these symptoms (controls).
A region in southern Sweden with a population of 170000.
A sex- and age-stratified sample of 3000 subjects (age range, 25-74 years) was randomly selected from the general population register and sent the survey, with a response rate of 83% (n = 2466; 46% men). Of the symptomatic responders, 81% underwent clinical examination.
Population prevalence rates, calculated as the number of symptomatic responders diagnosed on examination as having clinically certain CTS and/or electrophysiological median neuropathy divided by the total number of responders.
Of the 2466 responders, 354 reported pain, numbness, and/or tingling in the median nerve distribution in the hands (prevalence, 14.4%; 95% confidence interval [CI], 13.0%-15.8%). On clinical examination, 94 symptomatic subjects were diagnosed as having clinically certain CTS (prevalence, 3.8%; 95% CI, 3.1%-4.6%). Nerve conduction testing showed median neuropathy at the carpal tunnel in 120 symptomatic subjects (prevalence, 4.9%; 95% CI, 4.1%-5.8%). Sixty-six symptomatic subjects had clinically and electrophysiologically confirmed CTS (prevalence, 2.7%; 95% CI, 2.1%-3.4%). Of 125 control subjects clinically examined, electrophysiological median neuropathy was found in 23 (18.4%; 95% CI, 12.0%-26.3%).
Symptoms of pain, numbness, and tingling in the hands are common in the general population. Based on our data, 1 in 5 symptomatic subjects would be expected to have CTS based on clinical examination and electrophysiologic testing.
BackgroundA prospective study of computer users was performed to determine the occurrence of and evaluate risk factors for neck or shoulder (N/S) and hand or arm (H/A) musculoskeletal symptoms (MSS) and disorders (MSD).Methods
Individuals (n = 632) newly hired into jobs requiring ≥ 15 hr/week of computer use were followed for up to 3 years. At study entry, workstation dimensions and worker postures were measured and medical and psychosocial risk factors were assessed. Daily diaries were used to document work practices and incident MSS. Those reporting MSS were examined for specific MSD. Incidence rates of MSS and MSD were estimated with survival analysis. Cox regression models were used to evaluate associations between participant characteristics at entry and MSS and MSD.ResultsThe annual incidence of N/S MSS was 58 cases/100 person-years and of N/S MSD was 35 cases/100 person-years. The most common N/S MSD was somatic pain syndrome. The annual incidence of H/A MSS was 39 cases/100 person-years and of H/A MSD was 21 cases/100 person-years. The most common H/A disorder was deQuervain's tendonitis. Forty-six percent of N/S and 32% of H/A MSS occurred during the first month of follow-up. Gender, age, ethnicity, and prior history of N/S pain were associated with N/S MSS and MSD. Gender, prior history of H/A pain, prior computer use, and children at home were associated with either H/A MSS or MSD.ConclusionsH/A and N/S MSS and MSD were common among computer users. More than 50% of computer users reported MSS during the first year after starting a new job. Am. J. Ind. Med. 41:221–235, 2002. © 2002 Wiley-Liss, Inc.
The social context of occupational disease -- Cumulative trauma disorders of the hands and wrists -- Back pain -- Noise-induced hearing loss -- Conclusion -- Appendixes -- References Bibliografía: P. 305-336
A cross-sectional study was conducted to assess the association of upper extremity musculoskeletal disorders and work-related factors among employees using video display terminals at a large metropolitan newspaper.
The study included 1050 randomly selected workers from four departments. The workers were asked to complete questionnaires on symptoms, job tasks, and psychosocial and work organization conditions. Musculoskeletal disorders of the upper extremities were defined by frequency, duration, and intensity of symptoms not attributable to acute injury. Data were analyzed with the use of logistic regression.
A total of 973 workers completed the survey. The one-year period prevalence rate for any musculoskeletal disorder of the upper extremities was 41%. Neck symptoms (26%) were the most frequently reported, followed by hand or wrist (22%), shoulder (17%), and elbow (10%) symptoms. Greater time working at the video display station was associated with increased hand or wrist symptoms in a dose-response relationship. In addition, variables corresponding to increased work-load demands (eg, increased time working under deadline and increased job pressure) were associated with increased neck, shoulder, and hand or wrist disorders. Women were more likely to report symptoms in several areas, but this finding may reflect the concentration of women in jobs involving more risk factors.
The results suggest a high prevalence of musculoskeletal disorders of the upper extremities among newspaper employees, and they provide additional evidence that increased work load, time pressure, and greater hours of computer use are related to the occurrence of work-related musculoskeletal disorders among these workers, particularly for disorders in the hand or wrist area.
The relationship between workplace factors and work-related upper extremity musculoskeletal disorders (UE disorders) was assessed in a cross-sectional study of 533 telecommunication employees utilizing video display terminals (VDTs). Cases of UE disorders were defined using symptom questionnaires and physical examinations. Data on demographics, individual factors (medical conditions and recreational activities), work organization and practices, and psychosocial aspects of work, including electronic performance monitoring (EPM), were obtained by questionnaire. Associations between workplace factors and UE disorders were assessed by multiple logistic models generated for each of the four UE areas (neck, shoulder, elbow, hand/wrists). One-hundred and eleven (22%) participants met our case definition for UE disorders. Probable tendon-related disorders were the most common (15% of participants). Probable nerve entrapment syndromes were found in 4% of participants. The hand/wrist was the area most affected, 12% of participants. The following variables had associations in the final models (p < 0.05) with at least one of the four UE disorders, although the strength of these associations were modest. Non-white race, a diagnosis of a thyroid condition (self-reported) use of bifocals at work, and seven psychosocial variables (fear of being replaced by computers, increasing work pressure, surges in workload, routine work lacking decision-making opportunities, high information processing demands, jobs which required a variety of tasks and lack of a production standard) were associated with UE disorders. This study indicates that work-related UE musculoskeletal disorders are relatively common among telecommunication workers who use VDTs, and adds to the evidence that the psychosocial work environment is related to the occurrence of these disorders.
We sought to determine the incidence rate of carpal tunnel syndrome in the general population. Using three different case definitions, we conducted a prospective study to ascertain by medical record review all cases of incident disease in a defined population during a 2-year period. Newly diagnosed probable or definite carpal tunnel syndrome (N = 309) occurred at a rate of 3.46 cases per 1,000 person-years (95% confidence interval = 3.07-3.84). The incidence rate in our study was 3.5 times higher than the rate 20 years ago in a Minnesota city. The rate difference probably results from a combination of reasons, including a true rise in incidence.
Work-related carpal tunnel syndrome (CTS) now accounts for more than 41% of all repetitive motion disorders in the United States. Carpal tunnel syndrome is also associated with obesity and many different medical diseases.
Two hundred ninety-seven patients medically certified with a work-related upper extremity industrial illness underwent a systematic search for concurrent medical diseases. Diagnoses of CTS were made using 4 separate case definitions.
One hundred nine separate atraumatic illnesses (mainly hypothyroidism, diabetes mellitus, and various arthropathies) capable of causing arm pain or CTS were diagnosed in a third of all patients. Using record reviews and patient histories alone, 68% of these conditions would have been missed. One hundred ninety-eight patients had been diagnosed as having CTS 420 times in more than 1000 office visits, but diagnostic laboratory studies were ordered only 25 times. Every case definition of CTS was significantly associated with a related medical condition. Two definitions yielded more than 41% prevalence of concurrent disease (odds ratio, > or = 2.36; P < or = .004), and up to two thirds of these patients had either a medical disease or were obese (odds ratio, > or = 3.15; P < or = .001). Two cohorts totaling 114 patients (38%) working for companies employing nearly 19,000 people included all CTS claims filed during 2 evaluation periods. They did not differ from the other patients with CTS with respect to age, concurrent disease, or obesity.
Routine patient histories and record reviews are inadequate for proper evaluation of work-related CTS. Unrecognized medical diseases capable of causing CTS are common. Studies asserting an association between occupational hand usage and CTS are of questionable validity unless they prospectively account for confounding disease and obesity.