***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: & NA ; A series of health surveys are conducted every sixth to seventh year in Denmark . In the most recent survey of 2000 , a national r and om sample ( > 16 years ) was drawn from the Danish Central Personal Register . Out of the original sample 12,333 ( 74 % ) were interviewed and of these 10,066 returned a completed question naire ( SF‐36 ) . The present study includes only those who both took part in the interview and the postal question naire . Cancer patients were excluded . Persons suffering from chronic pain ( PG ) were identified through the question ‘ Do you have chronic/long lasting pain lasting 6 months or more ’ ? An overall chronic pain prevalence of 19 % was found −16 % for men and 21 % for women . Prevalence of chronic pain increased with increasing age . Persons ≥67 years had 3.9 higher odds of suffering from chronic pain than persons in the age group 16–24 years . Compared with married persons , divorced or separated persons had 1.5 higher odds of chronic pain . Odds for chronic pain were 1.9 higher among those with an education of less than 10 years compared with individuals with an education of 13 years or more . During a 14‐day period reporters of chronic pain had an average of 0.8 days ( range 0–10 ) lost due to illness compared with an average of 0.4 days ( range 0–10 ) for the control group ( CG ) ( Odds Ratio ( OR ) ) 2.0 ) . Persons with a job which required high physical strain were more likely to report chronic pain compared with those with a sedentary job ( OR 2.2 ) . The odds of quitting one 's job because of ill health were seven times higher among people belonging to the PG . A strong association between chronic pain and poor self‐rated health was also demonstrated . The PG had twice as many contacts with various health professionals compared with the CG , and the health care system was , on average , utilised 25 % more ( overall contacts ) by the PG than by the general population . Among the persons in the PG , 33 % were not satisfied with the examinations carried out in connection with their pain condition and 40 % were not satisfied with the treatment offered . Nearly 130,000 adults , corresponding to 3 % of the Danish population , use opioids on a regular basis . Opioids are used by 12 % of the PG The role of gonadal hormones on pain sensations was investigated in normally menstruating women ( n = 16 ) using the cold pressor test .  Tolerance time , pain threshold , and pain intensity were examined once a week during a 4-wk period , and serum concentrations of 17beta-estradiol and progesterone were determined at each test session , which were classified into the early follicular phase , late follicular phase , early luteal phase , and late luteal phase , as determined by the first day of menses and the actual hormone levels recorded . A group of men ( n = 10 ) of the same age interval was examined for comparison . The data show that pain threshold was reduced during the late luteal phase compared with the late follicular phase , and hormone analyses showed significant positive correlation between the progesterone concentration and lowered pain threshold and increasing pain intensity . Hormone analysis also showed an interaction between S-estradiol and S-progesterone on pain intensity , demonstrating that the increased perceived pain intensity that was associated with high progesterone concentrations was significantly reduced with increasing levels of estradiol . While no statistically significant sex differences in pain measurements were found , women displayed much more pronounced , and statistically significant , session-to-session effects than men , with increased pain threshold and decreased pain intensity with each test session . Hence , these data suggest that the changes in the serum concentration of gonadal hormones that occur during the menstrual cycle influence pain sensations elicited by noxious tonic cold stimulation and show that adaptation to the cold pressor test may be sex dependent & NA ; Gender differences in pain habituation , temporal summation , and pressure hyperalgesia evoked by repeated injections of glutamate into the dominant trapezius muscle were investigated . The  glutamate‐evoked muscle pain intensity and pressure pain threshold ( PPT ) were assessed . The PPTs were measured bilaterally in the trapezius muscles ( local pain area ) and posterolateral neck muscles ( referred pain area ) after glutamate injection in healthy and age‐matched males and females ( each n=14 ) .  Two glutamate injections ( 0.4 ml , 2 M each ) were injected with an interval of 5 min . One injection of glutamate ( 0.4 ml , 2 M ) served as a control . Males , but not females , rated the second injection ( maximal pain intensity ) significantly less painful than the first injection . The area under the visual analogue scale pain curve of the second injection was significantly larger than the first injection in females . Repeated glutamate injections , but not one‐glutamate injection , significantly decreased PPTs in the local pain area , with no significant gender differences . No PPTs changes were observed either in the contralateral trapezius muscle or bilaterally in the referred pain areas in either sex . These results suggest that a less efficient pain habituation and a greater susceptibility to the development of temporal summation of muscle pain in females , but not in males , might be one of the contributing factors to the higher incidence of neck shoulder pain in females . In addition , the reduction of PPTs in the local pain area evoked by intramuscular glutamate injection may represent an early process of peripheral pressure hyperalgesia , which is most likely gender independent & NA ; Aims of investigation : To quantify the magnitude of putative gender differences in experimental pressure pain threshold ( PPT ) , and to establish the relevance of repeated measurements to any such differences . Methods : Two separate studies were undertaken . A pressure algometer was used in both studies to assess PPT in the first dorsal interosseous muscle . Force was increased at a rate of 5 N /s . In study 1 , two measurements were taken from 240 healthy volunteers ( 120 males , 120 females ; mean age 25 years ) giving a power for statistical analysis of & bgr;=0.80 at & agr;=0.01 . In study two , 30 subjects ( 15 males , 15 females mean age 28 years ) were r and omly selected from study one . Fourteen repeated PPT measurements were recorded at seven , 10 min intervals . Mean PPT data for gender groups , from both studies , were analysed using analysis of covariance with repeated measures , and age as the covariate . Results : The mean PPT for each of the two measurements in study one showed a difference between gender of 12.2 N ( f=30.5 N , m=42.7 N ) and 12.8 N ( f=29.5 N , m=42.3 N ) , respectively , representing a difference of 28 % with females exhibiting a lower threshold . In study two , the mean difference calculated from 14 PPT repeated measurements over a 1 h period was comparable to that in study one at 12.3 N ( range 10.4–14.4 N ) again females exhibited the lower threshold . The differences in mean PPT values between gender were found to be significant in both study one , at ( P<0.0005 , F=37.8 , df=1 ) and study two ( P=0.01 , F=7.6 , df=1 ) . No significant differences were found in either study with repeated measurement ( P=0.892 and P=0.280 ) , or on the interaction of gender and repeated measurement after controlling for age ( P=0.36 and P=0.62 ) . Conclusion : Healthy females exhibited significantly lower mean PPTs in the first dorsal interosseous muscle than males , which was maintained for fourteen repeated measures within a 1 h period . This difference is likely to be above clinical ly relevant levels of change , and it has clear implication s for the use of different gender subjects in laboratory based experimental design s utilising PPT as an outcome measure BACKGROUND AND PURPOSE Palpation of peripheral nerve trunks has been advocated as a method of assessing the presence of hyperalgesic nerve tissue as a contributing factor to pain syndromes in musculoskeletal disorders of the upper quadrant . This study investigated , in the first instance , the pressure pain thresholds of the median , radial and ulnar nerve trunks of the upper limb in healthy , asymptomatic subjects . METHOD Forty-five male and 50 female healthy volunteer subjects participated in this study which involved measurement of  pressure pain thresholds  by use of pressure algometry bilaterally over the three peripheral nerve trunks in the upper limbs . RESULTS Pressure pain thresholds were shown to be lowest in the median nerve ( p = 0.001 ) and lower in female subjects ( p = 0.001 ) . Laterality ( p = 0.077 ) or the age of the subject ( p = 0.254 ) did not significantly influence results . CONCLUSIONS The study demonstrated differences in pressure pain thresholds in the three nerve trunks of the upper limb . These findings should be taken into account when interpreting the findings of nerve palpation in musculoskeletal upper quadrant disorders Objectives : Evidence has accumulated that men and women show different responses to noxious stimuli , with women exhibiting greater sensitivity to pain than men . Data concerning sex differences in Cortisol response patterns have revealed inconsistent results so far . The purpose of the present study was to examine sex differences in subjective pain and Cortisol response to a noxious stressor . Methods : Seventy‐six subjects ( 39 male and 37 female ) were investigated by a modification of the cold pressor test that consisted of intermittent immersion of the h and into ice water ( plunge test , PT ) . The PT was conducted twice , in consecutive trials , to guarantee a sufficient exposure to the noxious stressor for eliciting Cortisol responses . In each trial , tolerance time and pain ratings visual analog scale ( VAS ) were assessed . Seven saliva sample s ( c1‐c7 ) were collected to determine Cortisol levels at baseline ( c1‐c2 ) , directly before ( c3 ) and 20 minutes after noxious stress ( c4 ) , and during recovery period ( c5‐c7 ) . Results : We found no significant sex differences in tolerance time in trial 1 , but highly significant differences in tolerance time in trial 2 , with higher tolerance times in men . No significant sex differences were found for the VAS ratings of pain intensity and unpleasantness in the 2 trials . In contrast , a significantly larger Cortisol increase in men was observed compared with women . Analysis of covariance revealed that this result could not be attributed to sex differences in Cortisol level at baseline and in tolerance time . Discussion : The present study demonstrates that men show a larger Cortisol response to a noxious stressor than women that is not attributable to sex differences in subjective pain . The conclusion of a causal relation between larger Cortisol responses and higher pain tolerance thresholds in men is tempting but yet speculative & NA ; The purpose of the present study was to determine whether gender differences exist in the forebrain cerebral activation patterns of the brain during pain perception . Accordingly , positron emission tomography ( PET ) with intravenous injection of H2 15O was used to detect increases in regional cerebral blood flow ( rCBF ) in normal right‐h and ed male and female subjects as they discriminated differences in the intensity of innocuous and noxious heat stimuli applied to the left forearm . Each subject was instructed in magnitude estimation based on a scale for which 0 indicated ‘ no heat sensation ’ ; 7 , ‘ just barely painful ’ and 10 , ‘ just barely tolerable ’ . Thermal stimuli were 40 ° C or 50 ° C heat , applied with a thermode as repetitive 5‐s contacts to the volar forearm . Both male and female subjects rated the 40 ° C stimuli as warm but not painful and the 50 ° C stimuli as painful but females rated the 50 ° C stimuli as significantly more intense than did the males ( P=0.0052 ) . Both genders showed a bilateral activation of premotor cortex in addition to the activation of a number of contralateral structures , including the posterior insula , anterior cingulate cortex and the cerebellar vermis , during heat pain . However , females had significantly greater activation of the contralateral prefrontal cortex when compared to the males by direct image subtraction . Volume of interest comparison ( t‐statistic ) also suggested greater activation of the contralateral insula and thalamus in the females ( P<0.05 ) . These pain‐related differences in brain activation may be attributed to gender , perceived pain intensity , or to both factors Objective : In contrast to the research using typical experimental pain stimuli , there is no consensus that women are more sensitive to delayed onset muscle pain than men . The purpose of this study was to examine sex differences in delayed onset muscle pain with use of a quantified stimulus intensity and multidimensional and valid pain measures . Methods : Ninety-five participants ( 49.5 % women ) completed eccentric exercise  and then returned to the laboratory at 24 and 48 hours postexercise . The same relative intensity of the eccentric exercise was administered to women and men based on their eccentric strength . Results : The occurrence of muscle pain was confirmed by increases in intensity , F2 , 182 = 162.28 , P<0.01 , η2 = 0.64 , and unpleasantness , F2 , 182 = 204.03 , P < 0.01 , η2 = 0.69 , and st and ardized pain ratings , F2 , 180 = 67.44 , P < 0.01 , η2 = 0.43 . The affective ratios indicated that the muscle pain was more unpleasant than intense . No sex differences were detected except that men reported higher affective ratios than women , F1 , 92 = 4.06 , P < 0.05 , η2 = 0.04 . Discussion : The absence of higher muscle pain ratings in women than men in this investigation 
    Output:
    
This review suggests that females ( F ) and males ( M ) have comparable thresholds for cold and ischemic pain , while pressure pain thresholds are lower in F than M. There is strong evidence that F tolerate less thermal ( heat , cold ) and pressure pain than M but it is not the case for tolerance to ischemic pain , which is comparable in both sexes .
The majority of the studies that measured pain intensity and unpleasantness showed no sex difference in many pain modalities .
In summary , 10 years of laboratory research have not been successful in producing a clear and consistent pattern of sex differences in human pain sensitivity , even with the use of deep , tonic , long-lasting stimuli , which are known to better mimic clinical pain .