***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 
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    Input: Objective . Gastroesophageal reflux disease has been reported to be a common burden on health-care re sources in the Western world , but its manifestations in the general population are as yet unclear . The aim of this study was to estimate the prevalence of , and to identify the risk factors for gastroesophageal reflux symptoms ( GERS ) and erosive esophagitis ( EE ) in the adult population of two Swedish municipalities . Material and methods . A r and om sample ( n=3000 ) of the adult population ( 20–81 years of age ) of two Swedish municipalities ( n=21,610 ) was surveyed using a vali date d postal question naire assessing gastrointestinal symptoms . The response rate was 74 % . A sub sample ( n=1000 ) of the responders was subsequently invited , in r and om order , for esophago-gastro-duodenoscopy with evaluation of GERS , risk factors and tests for Helicobacter pylori .  Results . GERS were reported by 40.0 % and EE was found in 15.5 % of the population that had undergone endoscopy . Of those with GERS , 24.5 % had EE while 36.8 % of those with EE reported no GERS . Hiatus hernia and obesity remained significant risk factors for GERS and /or EE , with or without symptoms in a main effect model ( OR up to 14 at EE ) . Those with active H. pylori infection had a higher risk of GERS without EE than those without H. pylori infection ( OR=1.71 ( 1.23–2.38 ) ) . Conclusions . GERS and EE ( of which one-third is asymptomatic ) are highly prevalent in the Swedish adult population . H. pylori infection seems to play a role in the manifestations of gastroesophageal reflux AIM To clarify the association between physical activity and  gastroesophageal reflux disease ( GERD ) in non-obese and obese people . METHODS A Swedish population -based  cross-sectional survey was conducted . Participants aged 40 - 79 years were r and omly selected from the Swedish Registry of the Total Population .  Data on physical activity , GERD , body mass index ( BMI ) and the covariates age , gender , comorbidity , education , sleeping problems , and tobacco smoking were obtained using vali date d question naires . GERD was self-reported and defined as heartburn or regurgitation at least once weekly , and having at least moderate problems from such symptoms . Frequency of physical activity was categorized into three groups : ( 1 ) " high " ( several times/week ) ; ( 2 ) " intermediate " ( approximately once weekly ) ; and ( 3 ) " low " ( 1 - 3 times/mo or less ) . Analyses were stratified for participants with " normal weight " ( BMI < 25 kg/m² ) , " overweight " ( BMI 25 to ≤ 30 kg/m² ) and " obese " ( BMI > 30 kg/m² ) . Multivariate logistic regression was used to calculate odds ratios ( ORs ) with 95 % confidence intervals ( CIs ) , adjusted for potential confounding by covariates . RESULTS Of 6969 eligible and r and omly selected individuals , 4910 ( 70.5 % ) participated .  High frequency of physical activity was reported by 2463 ( 50 % ) participants , GERD was identified in 472 ( 10 % ) participants , and obesity was found in 680 ( 14 % ) . There were 226 ( 5 % ) individuals with missing information about BMI . Normal weight , overweight and obese participants were similar regarding distribution of gender and tobacco smoking status , while obese participants were on average slightly older , had fewer years of education , more comorbidity , slightly more sleeping problems , lower frequency of physical activity , and higher occurrence of GERD . Among the 2146 normal-weight participants , crude point estimates indicated a decreased risk of GERD among individuals with high frequency of physical activity ( OR : 0.59 , 95 % CI : 0.39 - 0.89 ) , compared to low frequency of physical activity . However , after adjustment for potential confounding factors , neither intermediate ( OR : 1.30 , 95 % CI : 0.75 - 2.26 ) nor high ( OR : 0.99 , 95 % CI : 0.62 - 1.60 ) frequency of physical activity was followed by decreased risk of GERD . Sleeping problems and high comorbidity were identified as potential confounders . Among the 1859 overweight participants , crude point estimates indicated no increased or decreased risk of GERD among individuals with intermediate or high frequency of physical activity , compared to low frequency . After adjustment for confounding , neither intermediate ( OR : 0.75 , 95 % CI : 0.46 - 1.22 ) nor high frequency of physical activity were followed by increased or decreased risk of GERD compared to low frequency among nonobese participants . Sleeping problems and high comorbidity were identified as potential confounders for overweight participants . In obese individuals , crude ORs were similar to the adjusted ORs and no particular confounding factors were identified . Intermediate frequency of  physical activity  was associated with a decreased occurrence of GERD compared to low frequency of physical activity ( adjusted OR : 0.41 , 95 % CI : 0.22 - 0.77 ) . CONCLUSION Intermediate frequency of physical activity might decrease the risk of GERD  among obese individuals , while no influence of physical activity on GERD was found in non-obese people BACKGROUND Two types of reflux episodes have been identified : upright or daytime and supine or nocturnal . The population -based prevalence of symptoms of nocturnal gastroesophageal reflux disease ( GERD ) and the impact of those symptoms on health-related quality of life ( HRQL ) have not been established . METHODS A national r and om- sample telephone survey was conducted to estimate the prevalence of frequent GERD and nocturnal GERD-like symptoms and to assess the relationship between HRQL , GERD , and nocturnal GERD symptoms .  Respondents were classified as controls , subjects with symptomatic nonnocturnal GERD , and subjects with symptomatic nocturnal GERD .  The HRQL was assessed using the Medical Outcomes Study Short-Form 36 Health Survey ( SF-36 ) . RESULTS The prevalence of frequent GERD was 14 % , with an overall prevalence of nocturnal GERD of 10 % . Seventy-four percent of those with frequent GERD symptoms reported nocturnal GERD symptoms .  Subjects with nonnocturnal GERD had significant decrements on the SF-36 physical and mental component summary scores compared with the US general population . Subjects reporting nocturnal GERD symptoms were significantly more impaired than subjects reporting nonnocturnal GERD symptoms on both the physical component summary ( 38.94 vs 41 . 52 ; P<.001 ) and mental component summary ( 46.78 vs 49.51 ; P<.001 ) and all 8 subscales of the SF-36 ( P<.001 ) . Subjects with nocturnal GERD demonstrated considerable impairment compared with the US general population and chronic disease population s. Subjects with nocturnal GERD had significantly more pain than those with hypertension and diabetes ( P<.001 ) and similar pain compared with those with angina and congestive heart failure . CONCLUSIONS Nocturnal symptoms are commonly experienced by individuals who report frequent GERD symptoms . In addition , HRQL is significantly impaired in those persons who report frequent GERD symptoms , and HRQL impairment is exacerbated in those who report nocturnal GERD symptoms Symptoms suggestive of gastro-oesophageal reflux disease are very common . The aim of the study was to assess the prevalence of these symptoms and factors influencing them in an unselected adult population . A question naire was mailed to a r and om sample of 2500 people aged > or = 20 years . The questions concerned heartburn , regurgitation , dysphagia , chest and upper abdominal pain , as well as medication and medical consultations for these symptoms . Of the 1700 ( 68 % ) responders , 9 % had experienced heartburn on the day of response and 15 % , 21 % and 27 % during the preceding week , month and year , respectively . The corresponding figures for regurgitation were 5 , 15 , 29 and 45 % . During the past year 43 % of the study group had had no such symptoms . Age , overweight , pregnancy and cigarette smoking significantly influenced the prevalence of symptoms . Using daily heartburn and /or regurgitation as dominant indicators 10.3 % ( 95 % CI 12 - 11.7 ) of the responders had gastro-oesophageal reflux disease .  Medication ( most commonly antacids ) was used by only 16 % of the symptomatic people , and only 5.5 % had sought medical advice for symptoms during the past year . Thus , despite commonness of symptoms suggestive of gastro-oesophageal reflux disease only a minority of the individuals suffering from such symptoms use medication or have medical consultation BACKGROUND The prevalence of gastroesophageal reflux disease ( GERD ) in Asian population s is reported to be lower than that in the West . Population -based data on the prevalence and symptom profile of GERD in developing Caucasian countries is lacking . Our objective was to determine the prevalence of gastrointestinal symptoms and clinical spectrum of GERD in Tehran , northern Iran and their association with patient characteristics . METHODS One thous and seven hundred telephone numbers were r and omly selected from Tehran telephone directory using a simple r and om method . A two-step screening telephone survey was then performed . In each answered call a second rapid survey was done to select a subject 18 - 65 years old from that household . A vali date d question naire was then filled out for that individual . Patient characteristics ( age , education , and gender ) and history of acid regurgitation and heartburn during the last week , as well as the previous three months were inquired about . RESULTS Of the 1,700 selected numbers , 278 either did not answer or did not have an eligible case ; 220 refused to participate . A total of 1,202 subjects ( 42 % males , mean age : 36 years , range : 18 - 65 yr ) were surveyed . The prevalence of heartburn occurring monthly , weekly , and daily was 4.7 % ( CI95 % : 3.5 - 6.0 % ) , 1.6 % ( CI95 % : 1.0 - 2.5 % ) , and 0.6 % ( CI95 % : 0.3 - 1.3 % ) , respectively . The corresponding figures for acid regurgitation were 15.6 % ( CI95 % : 13.6 - 17.7 % ) , 5.7 % ( CI95 % : 4.4 - 7.1 % ) and 1.5 % ( CI95 % : 0.9 - 2.4 % ) , respectively . The prevalence of GERD , defined as heartburn and /or acid regurgitation experienced daily , weekly and monthly was 1.9 % ( CI95 % : 1.2 - 2.9 % ) , 6.8 % ( CI95 % : 5.4 - 8.3 % ) , and 18.4 % ( CI95 % : 16.2 - 20.6 % ) . There was no relationship between the prevalence of GERD and either gender , age , or education . CONCLUSION Monthly GERD symptoms occur in 18.4 % of the general population in Tehran .  Acid regurgitation is more common ( 4 - 5 times ) than heartburn . Gender , age , and level of education do not affect the prevalence of GERD symptoms in the community studied Background We aim ed to determine the prevalence of gastroesophageal reflux disease ( GERD ) and associated risk factors , and assess quality of life ( QoL ) in relation to the frequency and severity of reflux symptoms . Methods A r and om sample of 1000 residents of Western Sydney were mailed a vali date d self-report question naire . GERD symptoms , risk factors , psychologic distress , QoL , and demographics were measured . Results The response rate was 73 % ( n=672 ; mean age , 46 y ; 52 % female ) . A total of 78 [ 12 % , 95 % confidence interval ( CI ) : 9 - 14 ] had GERD ( at least weekly heartburn and /or acid regurgitation ) . Independent risk factors for GERD were high cholesterol [ odds ratio ( OR ) = 3.28 , 95 % CI : 1.42 - 7.57 , P=0.005 ] and current smoker ( OR=2.47 , 95 % CI : 1.07 - 5.70 , P=0.03 ) . Anxiety , depression , and neuroticism were not risk factors . Worse physical functioning was the only QoL domain associated with GERD ( OR=0.98 , 95 % CI : 0.97 - 0.99 , P=0.006 ) . QoL was significantly impaired regardless of the severity of GERD for the QoL domains physical function , body pain , vitality , and social function . The frequency of heartburn and acid regurgitation were not associated with significantly reduced QoL domain scores . Conclusions Cardiac risk factors ( high cholesterol and smoking ) were independently associated with GERD . Increasing GERD symptom severity is associated with worse Q 
    Output:
    
Conclusions The prevalence of gastro-oesophageal reflux symptoms varied strikingly among countries , even when similar definitions were used to define their presence .
Prevalence was significantly higher in subjects ≥50 years , smokers , NSAID users and obese individuals , although these associations were modest