Tobacco Smoking Cessation and Improved GERD
Tobacco Smoking Cessation and Improved GERD
The study was based on a large population-based health study, the Nord-Trøndelag health study (the HUNT study), which we have used previously for epidemiological studies of GERS. The HUNT study is based on a series of health surveys where the entire population of Nord-Trøndelag County, Norway, from 20 years of age has been invited to participate. The first survey was conducted in 1984–1986 (HUNT 1), the second survey in 1995–1997 (HUNT 2), and the third survey in 2006–2008 (HUNT 3). In all surveys a basic questionnaire was accompanying the invitation letter and the participants were asked to meet at screening stations for clinical and laboratory examinations. A short questionnaire (Mini-Q) was sent to non-participants after HUNT 3 in 2009 and those who responded to the Mini-Q were also included in our study. The questionnaires and examinations included a wide range of health-related topics.
In HUNT 2 and HUNT 3/Mini-Q, GERS status of the participants was defined based on the participants' response to the following question: "To what degree have you had heartburn or acid regurgitation during the previous 12 months?" The question had three response alternatives: "No complaints," "Minor complaints," or "Severe complaints." Improvement in GERS status from severe GERS in HUNT 2 to no or minor GERS in HUNT 3/Mini-Q was defined as the study outcome, whereas severe GERS at both time points (stable GERS) were defined as reference. We have previously validated this GERS question and found that 25–31% of those reporting minor GERS and 95–98% of those reporting severe GERS had at least weekly complaints. This suggests that the majority of those reporting severe GERS actually have GERD according to the Montreal definition and classification of GERD.
In HUNT 2, the participants were asked about their tobacco smoking status by answering yes or no to these questions: "Have you ever smoked daily?," "Do you smoke cigarettes daily?," "Do you smoke cigars or cigarillos daily?," and "Do you smoke pipe daily?" In HUNT 3/Mini-Q, the participants were asked: "Do you smoke?" The response alternatives to this question were: "No, I have never smoked," "No, I have quit smoking," "Yes, cigarettes occasionally (parties/vacation, not daily)," or "Yes, cigarettes daily." Those who quitted daily tobacco smoking or reduced daily smoking to only occasional smoking between HUNT 2 and HUNT 3/Mini-Q were defined as "exposed" to tobacco smoking cessation, and those who were persistent daily tobacco smokers at both time points were regarded as "unexposed" to such cessation.
Covariables were selected based on their known association with GERS: sex, age, alcohol consumption, education, physical exercise, body mass index (BMI), and antireflux medication. Data on sex and age at participation were recorded at each survey. Average frequency of alcohol consumption and physical exercise was reported through questionnaires in HUNT 3/Mini-Q. Years of education were reported through questionnaires in HUNT 2. BMI was assessed by objectively measuring height and body weight under standardized conditions and by trained personnel at the screening stations in HUNT 2 and HUNT 3, whereas in Mini-Q height and weight were reported by the responders. BMI was calculated as body weight in kilograms divided by the square height in meters (kg/m). Antireflux medication included proton pump inhibitors, histamine-2-receptor antagonists, and antacids. In Norway, the prescription rules have until 2010 demanded a prescription from a physician to get proton pump inhibitors or histamine-2-receptor antagonists, except small packages of low-dose histamine-2-receptor antagonists that have been available over the counter. In this study, information was gathered on the participants' use of prescribed antireflux medication through the Norwegian Prescription Database (NorPD). The NorPD was established in 2004, and all prescribed medications from all Norwegian pharmacies were by legislation reported to the NorPD. From the NorPD data, the average use of prescribed antireflux medication was estimated based on the number of tablets prescribed during the HUNT 3 data collection period (2006–2008). In addition, the questionnaires in HUNT 3 included an assessment of over the counter medication use against several complaints, including heartburn or acid regurgitation. The question was: "How often have you used over the counter medication against the following complaints during the last month?" The participants responded with one of four alternatives to this question: "Rare/never," "1–3 times/week," "4–6 times/week," or "Daily." Thus, the two data sources were complementary with regard to the use of antireflux medication. There was no information on antireflux medication available during the HUNT 2 period.
Response rates were calculated from those eligible to participate at each survey, excluding those who were no longer residents in the county or had died. The association between tobacco smoking cessation (exposure) and GERS status (outcome) was assessed by multivariable logistic regression. Based on acknowledged criteria of a confounding factor, antireflux medication should not be included in the regression model, but instead be assessed as an effect modifier. To account for the effect of antireflux medication on GERS, the analyses were stratified by the use of antireflux medication, no or less than weekly use or at least weekly use, and the results were reported for each stratum separately. Participants with missing information on antireflux medication were analyzed as using no or less than weekly antireflux medication, because in the NorPD data it was not possible to distinguish between those with truly missing data and those who did not receive a prescription. Secondary analyses were also stratified by BMI using the categories defined by the World Health Organization: <18.5 (underweight), 18.5–24.9 (normal weight), 25.0–29.9 (preobese), and ≥30.0 (obese). To account for other potential confounders of the association between tobacco smoking and GERS, a continuous variable for age and categorical variables for sex, alcohol consumption (<weekly or ≥weekly), education (≤12 years or >12 years), and physical exercise (<weekly or ≥weekly) were included in the regression model. The statistical analyses were performed using Stata/IC 12.1 by StataCorp LP (College Station, TX).
The study was approved by the Regional Committee for Medical and Health Research Ethics, Central-Norway (ID 4.2009.328).
Methods
Study Design, Setting, and Participants
The study was based on a large population-based health study, the Nord-Trøndelag health study (the HUNT study), which we have used previously for epidemiological studies of GERS. The HUNT study is based on a series of health surveys where the entire population of Nord-Trøndelag County, Norway, from 20 years of age has been invited to participate. The first survey was conducted in 1984–1986 (HUNT 1), the second survey in 1995–1997 (HUNT 2), and the third survey in 2006–2008 (HUNT 3). In all surveys a basic questionnaire was accompanying the invitation letter and the participants were asked to meet at screening stations for clinical and laboratory examinations. A short questionnaire (Mini-Q) was sent to non-participants after HUNT 3 in 2009 and those who responded to the Mini-Q were also included in our study. The questionnaires and examinations included a wide range of health-related topics.
Assessment of the Outcome GERS
In HUNT 2 and HUNT 3/Mini-Q, GERS status of the participants was defined based on the participants' response to the following question: "To what degree have you had heartburn or acid regurgitation during the previous 12 months?" The question had three response alternatives: "No complaints," "Minor complaints," or "Severe complaints." Improvement in GERS status from severe GERS in HUNT 2 to no or minor GERS in HUNT 3/Mini-Q was defined as the study outcome, whereas severe GERS at both time points (stable GERS) were defined as reference. We have previously validated this GERS question and found that 25–31% of those reporting minor GERS and 95–98% of those reporting severe GERS had at least weekly complaints. This suggests that the majority of those reporting severe GERS actually have GERD according to the Montreal definition and classification of GERD.
Assessment of the Exposure Tobacco Smoking
In HUNT 2, the participants were asked about their tobacco smoking status by answering yes or no to these questions: "Have you ever smoked daily?," "Do you smoke cigarettes daily?," "Do you smoke cigars or cigarillos daily?," and "Do you smoke pipe daily?" In HUNT 3/Mini-Q, the participants were asked: "Do you smoke?" The response alternatives to this question were: "No, I have never smoked," "No, I have quit smoking," "Yes, cigarettes occasionally (parties/vacation, not daily)," or "Yes, cigarettes daily." Those who quitted daily tobacco smoking or reduced daily smoking to only occasional smoking between HUNT 2 and HUNT 3/Mini-Q were defined as "exposed" to tobacco smoking cessation, and those who were persistent daily tobacco smokers at both time points were regarded as "unexposed" to such cessation.
Assessment of Covariables
Covariables were selected based on their known association with GERS: sex, age, alcohol consumption, education, physical exercise, body mass index (BMI), and antireflux medication. Data on sex and age at participation were recorded at each survey. Average frequency of alcohol consumption and physical exercise was reported through questionnaires in HUNT 3/Mini-Q. Years of education were reported through questionnaires in HUNT 2. BMI was assessed by objectively measuring height and body weight under standardized conditions and by trained personnel at the screening stations in HUNT 2 and HUNT 3, whereas in Mini-Q height and weight were reported by the responders. BMI was calculated as body weight in kilograms divided by the square height in meters (kg/m). Antireflux medication included proton pump inhibitors, histamine-2-receptor antagonists, and antacids. In Norway, the prescription rules have until 2010 demanded a prescription from a physician to get proton pump inhibitors or histamine-2-receptor antagonists, except small packages of low-dose histamine-2-receptor antagonists that have been available over the counter. In this study, information was gathered on the participants' use of prescribed antireflux medication through the Norwegian Prescription Database (NorPD). The NorPD was established in 2004, and all prescribed medications from all Norwegian pharmacies were by legislation reported to the NorPD. From the NorPD data, the average use of prescribed antireflux medication was estimated based on the number of tablets prescribed during the HUNT 3 data collection period (2006–2008). In addition, the questionnaires in HUNT 3 included an assessment of over the counter medication use against several complaints, including heartburn or acid regurgitation. The question was: "How often have you used over the counter medication against the following complaints during the last month?" The participants responded with one of four alternatives to this question: "Rare/never," "1–3 times/week," "4–6 times/week," or "Daily." Thus, the two data sources were complementary with regard to the use of antireflux medication. There was no information on antireflux medication available during the HUNT 2 period.
Statistical Analysis
Response rates were calculated from those eligible to participate at each survey, excluding those who were no longer residents in the county or had died. The association between tobacco smoking cessation (exposure) and GERS status (outcome) was assessed by multivariable logistic regression. Based on acknowledged criteria of a confounding factor, antireflux medication should not be included in the regression model, but instead be assessed as an effect modifier. To account for the effect of antireflux medication on GERS, the analyses were stratified by the use of antireflux medication, no or less than weekly use or at least weekly use, and the results were reported for each stratum separately. Participants with missing information on antireflux medication were analyzed as using no or less than weekly antireflux medication, because in the NorPD data it was not possible to distinguish between those with truly missing data and those who did not receive a prescription. Secondary analyses were also stratified by BMI using the categories defined by the World Health Organization: <18.5 (underweight), 18.5–24.9 (normal weight), 25.0–29.9 (preobese), and ≥30.0 (obese). To account for other potential confounders of the association between tobacco smoking and GERS, a continuous variable for age and categorical variables for sex, alcohol consumption (<weekly or ≥weekly), education (≤12 years or >12 years), and physical exercise (<weekly or ≥weekly) were included in the regression model. The statistical analyses were performed using Stata/IC 12.1 by StataCorp LP (College Station, TX).
Study Approval
The study was approved by the Regional Committee for Medical and Health Research Ethics, Central-Norway (ID 4.2009.328).
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