***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: Distinguishing cohort studies from case series is difficult . We propose a conceptualization of  cohort studies  in systematic review s of comparative studies . The main aim of this conceptualization is to clarify the distinction between cohort studies and case series . We discuss the potential impact of the proposed conceptualization on the body of evidence and workload . All studies with exposure-based sampling gather multiple exposures ( with at least two different exposures or levels of exposure ) and enable calculation of relative risks that should be considered cohort studies in systematic review s , including non-r and omized studies . The term “ enables/can ” means that a predefined analytic comparison is not a prerequisite ( i.e. , the absolute risks per group and /or a risk ratio are provided ) . Instead , all studies for which sufficient data are available for re analysis to compare different exposures ( e.g. , sufficient data in the publication ) are classified as cohort studies .There are possibly large numbers of studies without a comparison for the exposure of interest but that do provide the necessary data to calculate effect measures for a comparison . Consequently , more studies could be included in a systematic review . Therefore , on the one h and , the outlined approach can increase the confidence in effect estimates and the strengths of conclusions . On the other h and , the workload would increase ( e.g. , additional data extraction and risk of bias assessment , as well as reanalyses ) Gravity  compensation ( GC )  of the arm is used to facilitate arm movements in conventional therapy as well as in robot-assisted rehabilitation of neurologically impaired persons . Positive effects of  GC  on Range of Motion ( ROM ) have been demonstrated in stroke . In Multiple Sclerosis ( MS ) , research regarding this topic is lacking . Since an active participation of the patient is required for effective training , full support of the arm might not be advisable . The present study reports on the development of a procedure to measure actively the individual need for GC  and to estimate the influence of GC  on ROM during reaching , lifting and transporting in severely affected Persons with MS ( PwMS ) . Ten PwMS were tested with the procedure for determination of  GC .  Maximal reaching movements were performed in a 3D space in three conditions : No support ( NS ) , with GC by the HapticMaster ( GC-HM ) and with GC by the HapticMaster combined with a sling suspension system ( GC-HMS ) . For the total sample , significant correlations were found between the amount of GC and clinical tests for upper limb function . In four subjects with severe arm dysfunction it was found that mean ROM is larger in the GC-HMS condition compared to the GC-HM condition , and in the GC-HM condition compared to the NS condition , suggesting positive effects of GC on active ROM in PwMS . Therefore , GC could have a positive effect on arm rehabilitation by enabling the PwMS to actively reach a larger ROM during training The objective of this study was to determine the utility of a passive gravity-balanced arm orthosis , the Wilmington robotic exoskeleton ( WREX ) , for patients with neuromuscular diseases . The WREX , a four-degrees-of-freedom functional orthosis , is energized by rubber b and s to eliminate gravity and is attached to the wheelchair . The development and clinical testing of WREX is described in this report . Seventeen patients ( 14 boys and 3 girls ) with muscular disabilities participated in the study . Ages ranged from 4 to 20 years . Criteria for inclusion included a weakened arm , use of a wheelchair , the ability to grasp and release objects , and the ability to provide feedback on device use . Testing consisted of administering the  Jebsen test of  h  and function  without WREX and then testing again after approximately two weeks of wearing the WREX orthosis . The timed results of each task within the test then were compared . Specific tasks related to vertical movement required less time to perform with the WREX . A large number of subjects were able to perform the Jebsen tasks with the WREX , where they were unable to perform the task without the WREX .  Patients can benefit from WREX because it increases their performance in daily living activities and makes many tasks possible . The range-of-motion in the patients ' arms increased considerably , while the time required to complete some of the Jebsen test tasks decreased . Most patients were very receptive to WREX , although a few were ambivalent Non-r and omised studies of the effects of interventions are critical to many areas of healthcare evaluation , but their results may be biased . It is therefore important to underst and and appraise their strengths and weaknesses . We developed ROBINS-I ( “ Risk Of Bias In Non-r and omised Studies - of Interventions ” ) , a new tool for evaluating risk of bias in estimates of the comparative effectiveness ( harm or benefit ) of interventions from studies that did not use r and omisation  to allocate units ( individuals or clusters of individuals ) to comparison groups . The tool will be particularly useful to those undertaking systematic review s that include non-r and omised studies Therapeutic trials in muscular dystrophy have often been inconclusive . A protocol has been design ed which selects patients with Duchenne muscular dystrophy and permits accurate measurement of their status . An integral part of the protocol is a system for checking on the consistency of the data obtained using a computer program OBJECTIVE To provide guidance on how systematic review authors , guideline developers , and health technology assessment practitioners should approach the use of the risk of bias in  nonr and omized studies of interventions ( ROBINS-I ) tool as a part of GRADE 's certainty rating process . STUDY DESIGN AND SETTING The study design and setting comprised iterative discussion s , testing in systematic review s , and presentation at GRADE working group meetings with feedback from the GRADE working group . RESULTS We describe where to start the initial assessment of a body of evidence with the use of ROBINS-I and where one would anticipate the final rating would end up . The GRADE accounted for issues that mitigate concerns about confounding and selection bias by introducing the upgrading domains : large effects , dose-effect relations , and when plausible residual confounders or other biases increase certainty . They will need to be considered in an assessment of a body of evidence when using ROBINS-I. CONCLUSION The use of ROBINS-I in GRADE assessment s may allow for a better comparison of evidence from r and omized controlled trials ( RCTs ) and nonr and omized studies ( NRSs ) because they are placed on a common metric for risk of bias . Challenges remain , including appropriate presentation of evidence from RCTs and NRSs for decision-making and how to optimally integrate RCTs and NRSs in an evidence assessment 
    Output:
    
Results : An overall effect size of 1.06 ( 95 % CI = 0.76 - 1.36 , p < 0.00001 ) was obtained , demonstrating that upper limbs assistive devices significantly improve the performance in activities of daily living in people with neuromuscular diseases .