***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: Knowledge concerning aetiologic hypotheses can be obtained through systematic review s of observational studies . In observational studies , heterogeneity between studies is expected , because of differences in study design and analysis . Data from observational studies have to be made comparable before pooling of results from component studies is possible . In this , definition of exposure and disease and adjustment for confounding have to be taken into account . Three methods to deal with heterogeneity are presented : ignoring ( fixed effects model ) , modelling ( r and om effects model ) and exploring ( meta regression ) . Any combination of data in meta- analysis of observational studies has to be based on statistical , method ological and clinical considerations . The same considerations are applied for the choice which method is used Making a blood donation , especially for first-time donors , can be a stressful experience . These feelings of stress may inhibit donors from returning . This paper applies stress theory to this particular problem . The effects of a stress management intervention ( the provision of music ) and previous donor experience were examined in relation to pre- and post-donation mood , environmental appraisal s and coping behaviour . Results indicated that the provision of music had detrimental effects on environmental appraisal s for those who have donated up to two times previously , but beneficial effects for those who had donated three times before . These effects were , to an extent , moderated by coping processes but not perceived control . It is recommended that the provision of music is not used as a stress management technique in the context of blood donation BACKGROUND Some blood donation-related adverse events ( AEs ) can negatively impact the blood donor return rate ( BDRR ) and decrease donor retention . STUDY DESIGN AND METHODS One-thous and r and omly selected whole-blood donors were interviewed 3 weeks after a 525-mL index whole-blood donation for seven AEs . The number of return visits and duration of follow-up were recorded for each of the 1000 donors . A negative binomial regression analysis was used to determine the contribution of the four most common AEs to the BDRR , and interactions between these AEs were also evaluated . RESULTS The four most common AEs were bruise alone ( 15.1 % ) , sore arm " alone " ( 7.0 % ) , fatigue " alone " ( 5.1 % ) , and donor reaction " alone " ( 4.2 % ) , where " alone " is defined to also include donors who had a bruise but no other AE . The estimated BDRR for donations without AEs was 1.32 visits per year . The estimated BDRRs for the four most common AEs were : bruise alone , 1.32 visits per year ; sore arm alone , 1.30 visits per year ( 2 % reduction in BDRR ) ; fatigue alone , 1.06 visits per year ( 20 % reduction in BDRR ) ; and donor reaction alone , 0.87 visits per year ( 34 % reduction in BDRR ) . The BDRR for donor reaction , fatigue , and sore arm together was 0.20 visits per year ( 85 % reduction in BDRR ) . CONCLUSION Donor reaction had the most negative impact on the BDRR . There appears to be a synergistic effect between donor reaction , fatigue , and sore arm . Theoretically , amelioration of some AEs has the potential to improve BDRRs BACKGROUND There are no reports in the transfusion medicine literature that describe adverse reactions and donor arm injuries after whole-blood donation based on solicited information . STUDY DESIGN AND METHODS The present study solicited adverse reaction and donor arm injury information from 1000 r and omly selected whole-blood donors approximately 3 weeks after the whole-blood donation .  Two 16-gauge phlebotomy needles in use were also compared . RESULTS Thirty-six percent of the donors had one or more adverse effects ( AEs ) . The most common systemic AEs were fatigue ( 7.8 % ) , vasovagal symptoms ( 5.3 % ) , and nausea and vomiting ( 1.1 % ) . The most common arm findings were bruise ( 22.7 % ) , arm soreness ( 10.0 % ) , and hematoma ( 1.7 % ) . Men were half as likely as women to have an AE ( 23 % AE vs. 48 % AE , p < 0.0001 ) . Repeat blood donors had fewer AEs than first-time blood donors ( 36 % AE vs. 47 % AE , p < 0.007 ) , and African-American donors had numbers of AEs similar to those of Caucasian donors ( 31 % AE vs. 38 % AE , p = 0.30 ) . The two phlebotomy needles did not differ in causing blood donor AEs . CONCLUSION AEs after donation and complaints may be more common than previously thought . The postdonation interview is a good tool for defining the blood donor 's experience . It can also be used to evaluate and potentially improve blood donor safety and comfort Aims : To present the available empirical evidence for the assumed position of the concept of work related fatigue as : ( 1 ) short term effect of the working day ; and ( 2 ) an intermediate variable between work dem and s and the development of subjective health complaints and sickness absence . Methods : Results from six single occupation studies , conducted between 1996 and 2002 , are presented . Work dem and s ( working hours , decision latitude , break control/autonomy , and mental , emotional , and physical dem and s ) were assessed through vali date d scales . Work related fatigue was represented and assessed by means of the need for recovery after working time scale in all studies . Subjective health complaints and duration of sickness absence were quantified with the same instruments in most studies as well . Both cross sectional studies ( four ) as well as prospect i ve studies ( two ; up to two years follow up ) were performed . Cross sectional data of 3820 workers , in total , were available . Prospect i ve data were accessible for 1200 workers in industry and health care . Models were tested with stepwise multiple regression analyses . Results : Strong associations between work dem and s and need for necovery were found in different occupations . The variance explained in need for recovery by work dem and s , age , and ( baseline ) need for recovery ranged between 14 % and 48 % in both types of studies . The amount of explained variance by work dem and s , age , and ( baseline ) need for recovery in subjective health complaints ranged between 24 % and 58 % in the different occupations . The prospect i ve data showed the prognostic value of need for recovery in relation to subjective health complaints ( in terms of psychosomatic complaints , emotional exhaustion , or sleep problems ) and duration of future sickness absence . Conclusions : The hypothesised role for work related fatigue as a link in the causal string of events , that is assumed to exist between repeated adverse work dem and s and the development of work related stress reactions , ( psychological ) overload and , eventually , health problems , was confirmed BACKGROUND The experience of unpleasant blood donation reactions ( e.g. , dizziness , nausea , and fainting ) has been linked to negative attitudes about donation and decreased likelihood of repeat donation . Consequently , interventions to reduce the adverse effects of blood donation are important and likely to increase donor retention . Based on laboratory studies suggesting that social support attenuates both physical and psychological responses to stress , the present study hypothesized that the presence of a supportive person during the donation process may help reduce reactions . STUDY DESIGN AND METHODS A final sample of 65 men and women with fewer than three prior donations was r and omly assigned to either donate blood as usual or donate with a supportive research assistant . Donors in the support condition were accompanied throughout the donation process by a female research assistant who provided encouragement , made reassuring remarks , and engaged in small talk . Donors in both conditions completed a series of questions to assess anxiety , experience of prefaint reactions , and willingness to provide a future donation . RESULTS Compared to st and ard donation controls , donors in the social support condition reported fewer prefaint reactions ( F(1,61 ) = 9.15 , p = 0.004 , eta(2)= 0.13 ) and greater likelihood of donating again within the next year ( Z = -1.70 , p < 0.05 , one-tailed ) . CONCLUSION Relatively novice donors report reduced reactions to blood donation when accompanied by a supportive individual , suggesting that social support may be a simple strategy to enhance the donation experience and possibly increase donor retention OBJECTIVES Complaints of prolonged fatigue are considered as a major health problem , as it can affect daily functioning and may lead to work disability . To increase knowledge about the effectiveness of interventions focussing on fatigued patients , a study was design ed to evaluate an established training programme for patients with prolonged fatigue . MATERIAL S AND METHODS Eighteen patients who reported fatigue to be one of their major health complaints and who were suffering from functional impairments attended a training programme of six weeks , three times a week . The training consisted mainly of physical endurance training , relaxation therapy and breathing exercises in rest . At baseline , time- and frequency-domain measures of heart rate variability ( HRV ) and respiration rate measurements were recorded during rest and during recovery after bicycle exercise . Furthermore , fatigue complaints were assessed with the Checklist Individual Strength ( CIS ) . These measurements were repeated at three weeks and six weeks from baseline . RESULTS After three weeks , HRV increased significantly in rest -- SDNN , i.e. st and ard deviation of normal beat-to-beat intervals ( p = 0.02 ) , very low frequency ( p = 0.04 ) and low frequency ( p = 0.04)-- and showed a positive trend in the remaining HRV components . No significant HRV changes during recovery were found . Respiration rate decreased significantly after six weeks during rest ( from 11.8 , SD = 4.65 to 8.1 , SD = 2.57 b x min-1 ) and during recovery ( from 15.1 , SD = 4.90 to 10.4 , SD = 2.97 b x min-1 ) . In all patients , CIS scores decreased after six weeks training ( from 106 , SD = 13.3 to 78 , SD = 21.8 , p = 0.001 ) . CONCLUSIONS The results suggest that a six-week training programme has a beneficial effect on physiological and subjective parameters in patients with severe complaints of fatigue 
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For instance , Bravo et al. investigated factors associated with  fainting and donating blood  and showed that vasovagal reactions are more common during or after phlebotomy than during registration 8 .
Newman et al. showed that donors who experienced an  adverse event were less likely to return to the blood centre9 .
In line with this , Veldhuizen et al. showed a strong association between reporting a vasovagal reaction and stopping donating , especially among men6 .
Adverse events may upset the donors , causing increased anxiety .
However , despite some indications that anxiety is increased before and during donating blood10 , it remains largely unclear what factors are associated with such a stress reaction .
We also hypothesised that a greater stress reaction would be associated with factors such as donation-related adverse events , e.g. bruises or fainting , as opposed to not experiencing such an event .
Knowing and identifying potential stressors could help to optimise the donation experience for the donor