Relation Between Gastroesophageal Reflux Symptoms and Socioeconomic Factors: A Population-Based Study (the HUNT Study)
2007; Elsevier BV; Volume: 5; Issue: 9 Linguagem: Inglês
10.1016/j.cgh.2007.04.009
ISSN1542-7714
AutoresCatarina Jansson, Helena Nordenstedt, Saga Johansson, Mari‐Ann Wallander, Roar Johnsen, Kristian Hveem, Jesper Lagergren,
Tópico(s)Helicobacter pylori-related gastroenterology studies
ResumoBackground & Aims: Gastroesophageal reflux constitutes a major public health problem in the Western world. Few population-based studies have addressed socioeconomic factors in relation to reflux. Methods: We conducted a case-control study based on 2 health surveys performed in the Norwegian county of Nord-Trondelag in 1984–1986 and 1995–1997, respectively. Reflux was assessed in the second survey, comprising 65,333 participants representing 70% of the county’s adult population. Among 58,596 persons responding to questions regarding reflux symptoms, 3153 persons reporting severe symptoms represented the cases, and 40,210 persons without symptoms represented the controls. Data collected in questionnaires included socioeconomic status (SES) based on occupation, education, and material deprivation; family situation; and potential confounders. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated from unconditional logistic regression in crude models and models adjusted for age, sex, smoking, and body mass. Results: The risk of reflux increased with decreasing levels of SES based on occupation, education, and material deprivation. Increased risks of reflux were seen among unskilled laborers (OR, 1.6; 95% CI, 1.3–2.0), skilled laborers (OR, 1.4; 95% CI, 1.1–1.7), and self-employed and farmers (OR, 1.3; 95% CI, 1.1–1.6). A 1.9-fold (95% CI, 1.7–2.2) increased risk of reflux was observed among persons with low education, compared with highly educated persons. Reflux was more common among materially deprived persons (OR, 3.4; 95% CI, 2.9–4.1). The results were similar in crude and adjusted models. Conclusions: This large population-based study reveals a link between low SES and reflux symptoms that is not explained by the known risk factors of smoking or obesity. This finding deserves further research. Background & Aims: Gastroesophageal reflux constitutes a major public health problem in the Western world. Few population-based studies have addressed socioeconomic factors in relation to reflux. Methods: We conducted a case-control study based on 2 health surveys performed in the Norwegian county of Nord-Trondelag in 1984–1986 and 1995–1997, respectively. Reflux was assessed in the second survey, comprising 65,333 participants representing 70% of the county’s adult population. Among 58,596 persons responding to questions regarding reflux symptoms, 3153 persons reporting severe symptoms represented the cases, and 40,210 persons without symptoms represented the controls. Data collected in questionnaires included socioeconomic status (SES) based on occupation, education, and material deprivation; family situation; and potential confounders. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated from unconditional logistic regression in crude models and models adjusted for age, sex, smoking, and body mass. Results: The risk of reflux increased with decreasing levels of SES based on occupation, education, and material deprivation. Increased risks of reflux were seen among unskilled laborers (OR, 1.6; 95% CI, 1.3–2.0), skilled laborers (OR, 1.4; 95% CI, 1.1–1.7), and self-employed and farmers (OR, 1.3; 95% CI, 1.1–1.6). A 1.9-fold (95% CI, 1.7–2.2) increased risk of reflux was observed among persons with low education, compared with highly educated persons. Reflux was more common among materially deprived persons (OR, 3.4; 95% CI, 2.9–4.1). The results were similar in crude and adjusted models. Conclusions: This large population-based study reveals a link between low SES and reflux symptoms that is not explained by the known risk factors of smoking or obesity. This finding deserves further research. Gastroesophageal reflux, characterized by heartburn and acid regurgitation, constitutes a major public health problem in the Western world.1Ofman J.J. The relation between gastroesophageal reflux disease and esophageal and head and neck cancers: a critical appraisal of epidemiologic literature.Am J Med. 2001; 111: 124S-129SAbstract Full Text Full Text PDF PubMed Google Scholar, 2Nocon M. Labenz J. Willich S.N. Lifestyle factors and symptoms of gastro-oesophageal reflux: a population-based study.Aliment Pharmacol Ther. 2006; 23: 169-174Crossref PubMed Scopus (154) Google Scholar About 10%–20% of the adult populations in most Western societies experience reflux symptoms at least weekly.3Locke 3rd, G.R. Talley N.J. Fett S.L. et al.Prevalence and clinical spectrum of gastroesophageal reflux: a population-based study in Olmsted County, Minnesota.Gastroenterology. 1997; 112: 1448-1456Abstract Full Text PDF PubMed Scopus (1893) Google Scholar, 4Diaz-Rubio M. Moreno-Elola-Olaso C. 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Schmitt C.M. et al.The burden of illness of gastro-oesophageal reflux disease: impact on work productivity.Aliment Pharmacol Ther. 2003; 17: 1309-1317Crossref PubMed Scopus (140) Google Scholar and is the strongest known risk factor for esophageal adenocarcinoma,9Chow W.H. Finkle W.D. McLaughlin J.K. et al.The relation of gastroesophageal reflux disease and its treatment to adenocarcinomas of the esophagus and gastric cardia.JAMA. 1995; 274: 474-477Crossref PubMed Scopus (337) Google Scholar, 10Lagergren J. Bergstrom R. Lindgren A. et al.Symptomatic gastroesophageal reflux as a risk factor for esophageal adenocarcinoma.N Engl J Med. 1999; 340: 825-831Crossref PubMed Scopus (2576) Google Scholar a cancer type with poor survival rates.11Parkin D.M. Bray F. Ferlay J. et al.Global cancer statistics, 2002.CA Cancer J Clin. 2005; 55: 74-108Crossref PubMed Scopus (17222) Google ScholarDespite its high prevalence, the etiology of gastroesophageal reflux is not yet fully understood,2Nocon M. Labenz J. Willich S.N. Lifestyle factors and symptoms of gastro-oesophageal reflux: a population-based study.Aliment Pharmacol Ther. 2006; 23: 169-174Crossref PubMed Scopus (154) Google Scholar and there are few population-based epidemiologic studies of potential risk factors for reflux. Because heritability only accounts for a minor part of the liability to reflux,12Cameron A.J. Lagergren J. Henriksson C. et al.Gastroesophageal reflux disease in monozygotic and dizygotic twins.Gastroenterology. 2002; 122: 55-59Abstract Full Text Full Text PDF PubMed Scopus (207) Google Scholar the main causes are probably environmental factors.2Nocon M. Labenz J. Willich S.N. Lifestyle factors and symptoms of gastro-oesophageal reflux: a population-based study.Aliment Pharmacol Ther. 2006; 23: 169-174Crossref PubMed Scopus (154) Google Scholar The factors found so far to be most strongly associated with an increased prevalence of reflux include old age,6Dent J. El-Serag H.B. Wallander M.A. et al.Epidemiology of gastro-oesophageal reflux disease: a systematic review.Gut. 2005; 54: 710-717Crossref PubMed Scopus (1414) Google Scholar obesity,2Nocon M. Labenz J. Willich S.N. Lifestyle factors and symptoms of gastro-oesophageal reflux: a population-based study.Aliment Pharmacol Ther. 2006; 23: 169-174Crossref PubMed Scopus (154) Google Scholar, 6Dent J. El-Serag H.B. Wallander M.A. et al.Epidemiology of gastro-oesophageal reflux disease: a systematic review.Gut. 2005; 54: 710-717Crossref PubMed Scopus (1414) Google Scholar, 13Nilsson M. Johnsen R. Ye W. et al.Obesity and estrogen as risk factors for gastroesophageal reflux symptoms.JAMA. 2003; 290: 66-72Crossref PubMed Scopus (373) Google Scholar, 14Mohammed I. Nightingale P. Trudgill N.J. Risk factors for gastro-oesophageal reflux disease symptoms: a community study.Aliment Pharmacol Ther. 2005; 21: 821-827Crossref PubMed Scopus (97) Google Scholar and tobacco smoking.2Nocon M. Labenz J. Willich S.N. Lifestyle factors and symptoms of gastro-oesophageal reflux: a population-based study.Aliment Pharmacol Ther. 2006; 23: 169-174Crossref PubMed Scopus (154) Google Scholar, 6Dent J. El-Serag H.B. Wallander M.A. et al.Epidemiology of gastro-oesophageal reflux disease: a systematic review.Gut. 2005; 54: 710-717Crossref PubMed Scopus (1414) Google Scholar, 14Mohammed I. Nightingale P. Trudgill N.J. Risk factors for gastro-oesophageal reflux disease symptoms: a community study.Aliment Pharmacol Ther. 2005; 21: 821-827Crossref PubMed Scopus (97) Google Scholar, 15Nilsson M. Johnsen R. Ye W. et al.Lifestyle related risk factors in the aetiology of gastro-oesophageal reflux.Gut. 2004; 53: 1730-1735Crossref PubMed Scopus (233) Google Scholar Although a relation between socioeconomic status (SES) and health is well-established in Western countries,16Adler N.E. Ostrove J.M. Socioeconomic status and health: what we know and what we don’t.Ann N Y Acad Sci. 1999; 896: 3-15Crossref PubMed Scopus (1030) Google Scholar, 17Marshall B. Chevalier A. Garillon C. et al.Socioeconomic status, social mobility and cancer occurrence during working life: a case-control study among French electricity and gas workers.Cancer Causes Control. 1999; 10: 495-502Crossref PubMed Scopus (31) Google Scholar, 18Isaacs S.L. Schroeder S.A. Class: the ignored determinant of the nation’s health.N Engl J Med. 2004; 351: 1137-1142Crossref PubMed Scopus (305) Google Scholar with decreasing SES being associated with a wide range of diseases,16Adler N.E. Ostrove J.M. Socioeconomic status and health: what we know and what we don’t.Ann N Y Acad Sci. 1999; 896: 3-15Crossref PubMed Scopus (1030) Google Scholar few studies have examined socioeconomic factors in relation to reflux.The aim of our study was to investigate possible associations between socioeconomic factors and reflux symptoms by using a large Norwegian population-based study.MethodsStudy Design, Study Participants, and Data CollectionThis case-control study, described in detail elsewhere,13Nilsson M. Johnsen R. Ye W. et al.Obesity and estrogen as risk factors for gastroesophageal reflux symptoms.JAMA. 2003; 290: 66-72Crossref PubMed Scopus (373) Google Scholar derives from a cross-sectional study design (Figure 1). In brief, in the Norwegian county of Nord-Trondelag 2 consecutive population-based health surveys have been performed. The first (Helseundersokelse i Nord-Trondelag [HUNT 1]) was conducted during the period 1984–1986 and the second one (HUNT 2) during the years 1995–1997.19Holmen J. Midthjell K. Krüger O. et al.The Nord-Trondelag Health Study 1995-97 (HUNT 2): objectives, contents, methods and participation.Norsk Epidemiologi. 2003; 13: 19-32Google Scholar The residents of Nord-Trondelag county are essentially representative of the Norwegian population as a whole, but the average income and level of education are slightly lower than the national average.20Krokstad S. Westin S. Health inequalities by socioeconomic status among men in the Nord-Trondelag Health Study, Norway.Scand J Public Health. 2002; 30: 113-124PubMed Google Scholar Ninety-seven percent of the residents are white. The large amount of information collected from each study participant and the large number of participants covering an entire county population make the HUNT surveys among the largest health studies ever performed.19Holmen J. Midthjell K. Krüger O. et al.The Nord-Trondelag Health Study 1995-97 (HUNT 2): objectives, contents, methods and participation.Norsk Epidemiologi. 2003; 13: 19-32Google Scholar In HUNT 2, of 92,808 county residents age 20 years or older who were eligible, 65,333 persons (70%) participated. A total of 47,556 persons participated in both HUNT 1 and HUNT 2. Data were collected through extensive questionnaires and physical examinations. Informed consent was obtained from each participant. The research was approved by the Regional Committee for Medical Research Ethics, Region IV, Norway. The Norwegian Data Inspectorate approved the establishment of a research register.Definition of Cases and ControlsReflux symptoms were assessed in HUNT 2 only. The study questionnaire included 1 question regarding the experience of symptoms of heartburn or acid regurgitation during the past 12 months, with the response alternatives: (1) no symptoms, (2) minor symptoms, and (3) severe symptoms. Among the 58,596 persons (90%) who answered this question, 40,210 (69%) reported no symptoms, 15,233 (26%) reported minor symptoms, and 3153 (5%) reported severe symptoms. The 3153 persons with severe symptoms were selected to represent the case group, and the 40,210 persons without reflux symptoms were chosen as controls.13Nilsson M. Johnsen R. Ye W. et al.Obesity and estrogen as risk factors for gastroesophageal reflux symptoms.JAMA. 2003; 290: 66-72Crossref PubMed Scopus (373) Google Scholar The 15,233 persons reporting minor symptoms were excluded from the analyses. This exclusion was based on our previously conducted validation study comprising 1102 outpatients from the Nord-Trondelag county in Norway and the Karolinska University Hospital in Sweden, described previously in detail.13Nilsson M. Johnsen R. Ye W. et al.Obesity and estrogen as risk factors for gastroesophageal reflux symptoms.JAMA. 2003; 290: 66-72Crossref PubMed Scopus (373) Google Scholar In that study the question regarding reflux symptoms used in HUNT 2 was compared with an extensive, validated questionnaire, and we found that the symptom pattern in the group reporting minor symptoms was heterogeneous, which implied an increased risk of misclassification of the outcome, compared with the group with severe symptoms.13Nilsson M. Johnsen R. Ye W. et al.Obesity and estrogen as risk factors for gastroesophageal reflux symptoms.JAMA. 2003; 290: 66-72Crossref PubMed Scopus (373) Google Scholar Moreover, although heartburn and acid regurgitation are considered the cardinal symptoms of reflux, and the use of questionnaires to assess these symptoms is a validated measure of the true occurrence of reflux,21Klauser A.G. Schindlbeck N.E. Muller-Lissner S.A. Symptoms in gastro-oesophageal reflux disease.Lancet. 1990; 335: 205-208Abstract PubMed Scopus (699) Google Scholar, 22Locke G.R. Talley N.J. Weaver A.L. et al.A new questionnaire for gastroesophageal reflux disease.Mayo Clin Proc. 1994; 69: 539-547Abstract Full Text Full Text PDF PubMed Scopus (396) Google Scholar, 23Shaw M.J. Talley N.J. Beebe T.J. et al.Initial validation of a diagnostic questionnaire for gastroesophageal reflux disease.Am J Gastroenterol. 2001; 96: 52-57Crossref PubMed Google Scholar we further evaluated the outcome in the validation study. We found that 95% of the patients with severe reflux symptoms in the validation study (corresponding to our case group) had experienced reflux symptoms at least once weekly, resulting in a specificity of 99.5% for reflux symptoms occurring at least once a week in our case group.13Nilsson M. Johnsen R. Ye W. et al.Obesity and estrogen as risk factors for gastroesophageal reflux symptoms.JAMA. 2003; 290: 66-72Crossref PubMed Scopus (373) Google ScholarData on Socioeconomic FactorsThe HUNT questionnaires included measures of SES based on occupation, education, and material deprivation as well as questions regarding the family situation. Data on SES based on occupation and education and on the family situation were collected in both HUNT 1 and HUNT 2, whereas data on material deprivation were collected only in HUNT 2.SES based on occupation was derived from each study participant’s self-reported present or previous occupation. The original questions included 10 or 9 (HUNT 2 and HUNT 1, respectively) occupational categories/response alternatives, and these were reclassified on the basis of an approximation of the international social class scheme, described in detail elsewhere.20Krokstad S. Westin S. Health inequalities by socioeconomic status among men in the Nord-Trondelag Health Study, Norway.Scand J Public Health. 2002; 30: 113-124PubMed Google Scholar This approximation was made possible by the fact that the occupational classification in the HUNT studies follows the usual approach of classifying people on the basis of their position in the labor market into a number of discrete groups.20Krokstad S. Westin S. Health inequalities by socioeconomic status among men in the Nord-Trondelag Health Study, Norway.Scand J Public Health. 2002; 30: 113-124PubMed Google Scholar Thus, the participants were allocated into 6 well-established socioeconomic classes: (1) higher-level employees, employers, and professionals (reference group), (2) intermediate employees, (3) lower-level employees, (4) other self-employed and farmers, (5) skilled laborers, and (6) unskilled laborers. We analyzed 2 variables regarding the study participant’s SES with both HUNT 2 and HUNT 1 data and 1 variable regarding the SES of the participant’s partner with HUNT 2 data.Educational level was classified in accordance with the Norwegian school system and duration of education, on the basis of questions regarding the highest achieved level of education (5 response alternatives in HUNT 2 and 8 in HUNT 1), into 3 categories24Hagen K. Zwart J.A. Svebak S. et al.Low socioeconomic status is associated with chronic musculoskeletal complaints among 46,901 adults in Norway.Scand J Public Health. 2005; 33: 268-275Crossref PubMed Scopus (57) Google Scholar: (1) high education (>13 years, reference group), (2) medium education (11–13 years), and (3) low education (0–10 years).Material deprivation was assessed in HUNT 2 by 1 question25Pikhart H. Bobak M. Rose R. et al.Household item ownership and self-rated health: material and psychosocial explanations.BMC Public Health. 2003; 3: 38Crossref PubMed Scopus (29) Google Scholar as to whether during the last year the study participant’s household had experienced difficulties in managing daily expenses such as costs of food, transportation, and housing, with 4 response alternatives: (1) no, never (reference group); (2) yes, on rare occasions; (3) yes, now and then; and (4) yes, often.Living with a partner was assessed from questions regarding the study participant’s family situation and was dichotomized into (1) yes (living with partner, ie, married or cohabitant, reference group) and (2) no (not living with partner).Statistical AnalysesOdds ratios (ORs) and 95% confidence intervals (CIs), estimated by unconditional logistic regression,26Breslow N.E. Day N.E. Statistical methods in cancer research. Volume I. The analysis of case-control studies. Oxford University Press, Oxford, UK2002Google Scholar were used to assess the association between socioeconomic factors and risk of reflux, with the PROC GENMOD procedure in SAS (SAS Institute Inc, Cary, NC).27SAS IIChanges and enhancements through Release 6.11. SAS Institute Inc, Cary, NC1996Google Scholar Each socioeconomic factor was evaluated separately in crude and adjusted models. The multivariable models were adjusted for variables known a priori to be independent risk factors for reflux, ie, age (in 10-year age groups), sex, tobacco smoking (duration in years of daily smoking in 3 categories: (1) never or <1 year [reference group], (2) 1–9 years, and (3) ≥10 years), and body mass index (BMI) (kg/m2, assessed through physical examinations, in 4 categories on the basis of the World Health Organization (WHO) classification of overweight and obesity: (1) 35 (severe obesity). These variables were cross-sectional except for smoking, in which lifetime exposure was assessed. We also evaluated the influence of occurrence of asthma (yes or no), frequency of meals of salted meat or fish (in 5 categories), extra salt on meals (in 4 categories), coffee use (in 4 categories), dietary fiber content (in 4 categories), regular physical exercise (in 5 categories), alcohol use (in 4 categories), and tea use (in 3 categories), but virtually no effects on the estimates of the socioeconomic factors were found, and these variables were not included in the final models. Participants with missing data on any of the covariates included in the models were excluded from the analyses. Each exposure was evaluated with the Wald test, which considers all categories of the variable and not just pairwise comparisons with the reference category.ResultsCharacteristics of the Study ParticipantsThe study comprised 3153 cases and 40,210 controls, ie, 43,363 participants in total, as described in the Methods section. Of these, 30,188 (2378 cases, 27,810 controls) participated in both HUNT 2 and HUNT 1. The case participants were on average slightly older than the control participants, whereas the sex distribution was similar between the groups. Smoking (≥10 years) and obesity (BMI >30) were more common among the cases (51% and 27%, respectively) than among the controls (39% and 12%, respectively) (data not shown).Distribution of Socioeconomic FactorsHigher-level employees, employers, and professionals constituted the least common SES group, with no major differences between cases (9%) and controls (10%) (HUNT 2 data, Table 1). More cases (26%) than controls (13%) reported having difficulties in managing daily expenses (Table 1). The majority of all participants had a low educational level, but this was most common among the cases (81%), whereas having a high education was more common among the controls (24%) (HUNT 2 data, Table 1). The majority (82%) of all participants were married or cohabitant (Table 1).Table 1Socioeconomic Factors and Reflux SymptomsaObservations missing any covariate included in any of the models were excluded from the analyses.Socioeconomic factorCases n (%)Controls n (%)Crude OR (95% CI)Adjusted ORbObservations missing any covariate included any of the models were excluded from the analyses. Rs adjusted for age, sex, smoking, and BMI. (95% CI)SEScSES based on self-reported present or previous occupation, classified into 6 categories according to the international social class scheme. 1277 cases (41%) and 14,558 controls (36%) had missing data on SES because of persons reporting >1 occupation. (HUNT 2) Higher-level employees, employers, professionals163 (9)2548 (10)1.0 (reference)1.0 (reference) Intermediate employees217 (12)4845 (20)0.7 (0.6–0.9)0.9 (0.7–1.1) Lower-level employees336 (19)5467 (22)1.0 (0.8–1.2)1.1 (0.9–1.4) Other self-employed and farmers382 (21)4361 (18)1.4 (1.1–1.7)1.3 (1.1–1.6) Skilled laborers269 (15)3043 (12)1.4 (1.1–1.7)1.4 (1.1–1.7) Unskilled laborers438 (24)4272 (17)1.6 (1.3–1.9)1.6 (1.3–2.0)PdWald test of overall effect across all exposure strata. < .0001P < .0001SESeSES based on self-reported present or previous occupation, classified into 6 categories according to the international social class scheme. 1546 cases (49%) and 19,965 controls (50%) had missing data on SES. (HUNT 1) Higher-level employees, employers, professionals100 (7)1537 (8)1.0 (reference)1.0 (reference) Intermediate employees142 (9)3007 (16)0.7 (0.6–0.9)0.9 (0.7–1.1) Lower-level employees303 (20)4559 (24)1.0 (0.8–1.3)1.1 (0.9–1.5) Other self-employed and farmers431 (29)4653 (24)1.4 (1.1–1.8)1.4 (1.1–1.8) Skilled laborers210 (14)2338 (12)1.4 (1.1–1.8)1.4 (1.1–1.8) Unskilled laborers321 (21)3023 (16)1.6 (1.3–2.1)1.6 (1.3–2.0)P < .0001P < .0001Partner’s socioeconomic statusfStudy participant’s partner’s SES based on occupation. 1754 cases (56%) and 21,147 controls (53%) had missing data on partner’s SES. (HUNT 2) Higher-level employees, employers, professionals108 (8)2139 (12)1.0 (reference)1.0 (reference) Intermediate employees198 (15)3558 (19)1.1 (0.9–1.4)1.0 (0.8–1.2) Lower-level employees264 (20)3304 (18)1.6 (1.3–2.0)1.2 (0.9–1.5) Other self-employed and farmers280 (21)3757 (21)1.5 (1.2–1.9)1.2 (1.0–1.5) Skilled laborers204 (15)2618 (14)1.5 (1.2–2.0)1.4 (1.1–1.8) Unskilled laborers291 (22)2894 (16)2.0 (1.6–2.5)1.5 (1.2–1.9)P < .0001P < .0001Educationg1 question: “What education is the highest you have completed?”; 5 response alternatives categorized into high, medium, or low education. 164 cases (5%) and 1369 controls (3%) had missing data on education. (HUNT 2) High (>13 y)342 (12)8690 (24)1.0 (reference)1.0 (reference) Medium (11–13 y)194 (7)4085 (11)1.2 (1.0–1.4)1.3 (1.1–1.5) Low (≤10 y)2292 (81)24,008 (65)2.4 (2.2–2.7)1.9 (1.7–2.2)P < .0001P < .0001Educationh1 question: “What education is the highest you have completed?”; 8 response alternatives categorized into high, medium, or low education. 1189 cases (38%) and 17,150 controls (43%) had missing data on education. (HUNT 1) High (>13 y)109 (6)2900 (13)1.0 (reference)1.0 (reference) Medium (11–13 y)72 (4)1624 (8)1.2 (0.9–1.6)1.5 (1.3–1.7) Low (≤10 y)1639 (90)17,050 (79)2.6 (2.1–3.1)2.1 (1.9–2.4)P < .0001P < .0001Material deprivationi1 question: “Has your household during the last year had difficulties in managing daily expenses such as food, transportation, housing and the like?”; 4 response alternatives: no/rarely/sometimes/often. 967 cases (31%) and 11,063 controls (28%) had missing data regarding this question. (HUNT 2) No economic problems1191 (57)19,940 (72)1.0 (reference)1.0 (reference) Rarely economic problems361 (17)4232 (15)1.4 (1.3–1.6)1.5 (1.3–1.7) Sometimes economic problems350 (17)2718 (10)2.2 (1.9–2.4)2.1 (1.9–2.4) Often economic problems188 (9)895 (3)3.5 (3.0–4.2)3.4 (2.9–4.1)P < .0001P < .0001Living with partnerj1 question: “Who do you live with?”; response alternatives: husband/wife/cohabitant or living alone. 620 cases (20%) and 8396 controls (21%) had missing data regarding this question. (HUNT 2) Yes1952 (82)24,639 (82)1.0 (reference)1.0 (reference) No428 (18)5459 (18)1.0 (0.9–1.1)1.1 (0.9–1.2)P = .85P = .39Living with partnerk1 question: “Do you live alone or do you live together with other people?”; response alternatives: husband/wife/cohabitant or living alone. 1307 cases (41%) and 18,574 controls (46%) had missing data regarding this question. (HUNT 1) Yes1545 (91)18,531 (92)1.0 (reference)1.0 (reference) No160 (9)1713 (8)1.1 (0.9–1.3)1.1 (0.9–1.3)P = .19P = .47a Observations missing any covariate included in any of the models were excluded from the analyses.b Observations missing any covariate included any of the models were excluded from the analyses. Rs adjusted for age, sex, smoking, and BMI.c SES based on self-reported present or previous occupation, classified into 6 categories according to the international social class scheme. 1277 cases (41%) and 14,558 controls (36%) had missing data on SES because of persons reporting >1 occupation.d Wald test of overall effect across all exposure strata.e SES based on self-reported present or previous occupation, classified into 6 categories according to the international social class scheme. 1546 cases (49%) and 19,965 controls (50%) had missing data on SES.f Study participant’s partner’s SES based on occupation. 1754 cases (56%) and 21,147 controls (53%) had missing data on partner’s SES.g 1 question: “What education is the highest you have completed?”; 5 response alternatives categorized into high, medium, or low education. 164 cases (5%) and 1369 controls (3%) had missing data on education.h 1 question: “What education is the highest you have completed?”; 8 response alternatives categorized into high, medium, or low education. 1189 cases (38%) and 17,150 controls (43%) had missing data on education.i 1 question: “Has your household during the last year had difficulties in managing daily expenses such as food, transportation, housing and the like?”; 4 response alternatives: no/rarely/sometimes/often. 967 cases (31%) and 11,063 controls (28%) had missing data regarding this question.j 1 question: “Who do you live with?”; response alternatives: husband/wife/cohabitant or living alone. 620 cases (20%) and 8396 controls (21%) had missing data regarding this question.k 1 question: “Do you live alone or do you live together with other people?”; response alternatives: husband/wife/cohabitant or living alone. 1307 cases (41%) and 18,574 controls (46%) had missing data regarding this question. Open table in a new tab Associations Between Socioeconomic Factors and Reflux SymptomsThe results from the crude and adjusted models are presented in Table 1. The number of missing observations for the socioeconomic variables, except for education in HUNT 2, was fairly large (20%–56%), but there were no major differences between the cases and controls (Table 1).Socioeconomic status based on occupationThe risk of reflux increased moderately with decreasing levels of SES based on occupation (Table 1). A dose-response association was observed in both the crude and adjusted models on the basis of both HUNT 2 and HUNT 1 data. We found positive associations between low SES and risk of reflux among unskilled laborers (OR, 1.6; 95% CI, 1.3–2.0, adjusted model, HUNT 2 data), skilled laborers (OR, 1.4; 95% CI, 1.1–1.7, adjusted model, HUNT 2 data), and other self-employed and farmers (OR, 1.3; 95% CI, 1.1–1.6, adjusted model, HUNT 2 data) compared with higher-level employees (Table 1).Similar dose-response associations were seen between low SES based on occupation of the study participant’s partner and an increased risk of reflux (Table 1).EducationEducation was inv
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