***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: A system has been constructed to evaluate the design , implementation , and analysis of  r and omized control trials ( RCT ) . The degree of quadruple blinding ( the r and omization process , the physicians and patients as to therapy , and the physicians as to ongoing results ) is considered to be the most important aspect of any trial . The analytic techniques are scored with the same emphasis as is placed on the control of bias in the planning and implementation of the studies . Description of the patient and treatment material s and the measurement of various controls of quality have less weight . An index of quality of a RCT is proposed with its pros and cons . If published papers were to approximate these principles , there would be a marked improvement in the quality of r and omized control trials . Finally , a reasonable st and ard design and conduct of trials will facilitate the interpretation of those with conflicting results and help in making valid combinations of undersized trials The prevalence of  mild and severe radiological osteoarthritis  was investigated in a r and om sample of 6585 inhabitants of a Dutch village . Radiographs were grade d 0 - 4 according to the criteria described by Kellgren and Lawrence . The prevalence of radiological osteoarthritis increased strongly with age and was highest for cervical spine ( peak : men 84.8 % , women 84.3 % ) , lumbar spine ( peak : 71.9 % , women 67.3 % ) , and distal interphalangeal joints of the h and s ( peak : men 64.4 % , women 76 % ) . Prevalence did not exceed 10 % in sacroiliac joints , lateral carpometacarpal joints , and tarsometatarsal joints . Severe radiological osteoarthritis ( grade 3 or grade 4 ) was uncommon under age 45 ; in elderly persons the prevalence of severe radiological osteoarthritis did not exceed 20 % except for the cervical and lumbar spine , distal interphalangeal joints of the h and s and , in women only , metacarpophalangeal joints , first carpometacarpal joints , first metatarsophalangeal joints , and knees . Overall , differences between men and women were small except for hips and knees ; however , severe radiological osteoarthritis was found in a higher proportion in most of the joints in women . Our data were compared with data from similar population surveys . The slope between joint involvement and age was strikingly constant for most of the joints . Differences between population s were mainly differences in level . These differences of prevalence of radiological osteoarthritis may be attributed to interobserver differences -- that is , different criteria used to establish radiological osteoarthritis , in addition to genetic or environmental factors , or both We investigated in a case-referent study the relationship between arthrosis of the hip in women and lifestyle factors such as body mass index ( BMI ) , smoking and hormone therapy . The study comprised all women of ages 50 - 70 years , living in 5 counties and 5 towns in Sweden 1991 - 1994 . The cases ( n 230 ) were women with total hip replacements ( THR ) because of primary arthrosis , and the referents ( n 273 ) were r and omly selected women from the study base , without hip problems . All women were interviewed about height , weight , smoking habits , hormone therapy , sports activities , occupational history , home work , etc , to the age of 50 . The relative risk of developing hip arthrosis leading to a THR after the age of 50 was associated with an increased BMI . The highest value , 2.9 ( Cl 1.3 - 6.5 ) , was reported in those with BMI > or = 25 at the age of 40 . The preventive value of weight loss seems substantial . There was a greater risk of 1.5 ( Cl 1.0 - 2.2 ) for smokers than for non-smokers . Use of contraceptive pills meant an increase in the relative risk for THR , unlike estrogen substitution which was associated with a lower risk than in unexposed persons OBJECTIVES The aim of this study was to estimate the impact of physical work load , sports , and overweight on the incidence of coxarthrosis .  METHODS A case-referent study was made of 239 male recipients of a hip prosthesis and 302 men r and omly selected from the general population . Information was obtained by means of an interview and question naire . Exposures to physical work load and sports were measured as the cumulative number of hours of exposure up to 49 years of age . Overweight was measured as the estimated body mass index at 30 or 40 years of age . RESULTS The etiologic fraction related to the three risk factors was 40 % for physical work load , 55 % for sports , and 15 % for overweight . Various measures of physical work load were considered , but they all proved to be correlated . CONCLUSIONS Approximately 80 % of the idiopathic coxarthrosis was explained by the presence of the three risk factors In a case-control study , body-mass index ( BMI ) at aged 20 , 30 , 40 , and 50 years was studied in 239 men who had just received a hip prosthesis because of coxarthrosis and in 302 controls r and omly selected from the general population . Information about weight , occupational physical load , sports activities , smoking , and many other factors was self-reported in a question naire . Men with a BMI greater than the mean BMI + 1 SD had an increased relative risk of developing severe coxarthrosis as compared with men with a BMI less than the mean BMI -1 SD . Those slightly obese at the aged 40 years had a relative risk of 2.5 for later surgery of the hip 
    Output:
    
The associations between obesity and hip OA were , however , stronger in studies in which the diagnosis of hip OA was based not only on radiological criteria but also on clinical symptoms .
The evidence for a positive influence of obesity on the development of hip OA  is moderate