Accepted Article
Title: Physical fitness and amount of asthma and asthma like symptoms from childhood to adulthood 1 Running head: Fitness, asthma and asthma like symptoms during three decades. Jørgen Guldberg–Møller1;
Bob Hancox2; Dennis Mikkelsen3; Henrik Steen Hansen3; Finn
Rasmussen§4
1.
Department of Respiratory Medicine, Roskilde Hospital, Denmark
2.
Department of Preventive & Social Medicine, Dunedin School of Medicine, University of
Otago, New Zealand.
3.
Department of Cardiology, Odense University Hospital, Sdr. Boulevard, 5000 Odense C;
Denmark
4.
Department of Allergy, Respiratory and Sleep Medicine, Near East University Hospital,
Yakin Dogu Bulvarı , Nicosia, Mersin 10, Turkey.
§ Address correspondence to: Finn Rasmussen, MD, PhD, DMSc; Department of Allergy and Respiratory Medicine, Near East University Hospital, Yakin Dogu Bulvarı; Nicosia, Mersin 10, Turkey. Tel: +90 392 675 1000; Fax: +90 392 223 6461, E-mail: [email protected] Keyword: physical activity, respiratory symptoms, asthma, longitudinal. Word Count: 2536
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/crj.12145
This article is protected by copyright. All rights reserved.
1
Accepted Article Abstract:
The potential benefits of physical activity on the development of respiratory symptoms are not well known.
Objective: The present study investigated the longitudinal association between physical fitness and the development of asthma-like symptoms from childhood to adulthood in a longitudinal community based study. Methods: Participants were assessed at ages 9, 15, 20, and 29 years. Asthma-like symptoms and physical fitness was assessed at each age. Results: Tracking for physical fitness was high from age 9 to 29 years. Using logistic regression,
high physical fitness at age 9 predicted a lower prevalence of asthma like symptoms at ages 9, 20, and 29 years. Asthma at age 9 and female sex and smoking at any age were also independently associated with the presence of asthma like symptoms. Our findings suggest that the risk for the development of asthma is reduced by 3% and of asthma-like symptoms reduced by 2% from early
adolescence to young adulthood (age 9 years to age 29 years) by increasing the maximal workload with 1 W.kg-1.
Conclusion: This finding provide further evidence of a possible beneficial effect of physical activity in childhood on the development of respiratory symptoms in adulthood and supports the notion that the lower levels of physical activity in recent decades may have contributed to an increase in the
prevalence of asthma and asthma like symptoms.
This article is protected by copyright. All rights reserved.
2
Accepted Article
Introduction It is evident that the prevalence of asthma has increased during recent decades (1-4) and there has been focus on whether this could be due to changes in lifestyle factors in westernised countries such as physical activity, allergen exposure, diet, and obesity. A growing body of evidence has shown an association between obesity and a higher prevalence of asthma (5, 6). Obesity is closely associated with low levels of physical activity and some studies (7) have suggested that physical inactivity is an independent risk factor for asthma apart from obesity. The evidence concerning the association between physical activity and asthma is sparse, but a recent review pointed out that the available
evidence indicates that physical activity is a possible protective factor against asthma development
(8). In the Odense Schoolchild Study we have previously shown an association between poor physical fitness in childhood and asthma development in young adulthood (9). Physical activity has been decreasing in westernised countries in the same time as the recent
increases in asthma prevalence have occurred so it is reasonable to ask if physical activity plays a role in preventing persistent asthma and asthma-like symptoms. Few cross-sectional studies are available, some of which have reported an association between higher levels of physical activity and a lower prevalence of asthma symptoms (10,11) whereas others have not (12-15). These studies differ in outcome measures and suffer the inherent problem of cross-sectional designs of being
unable to establish the temporal sequence: whether physical inactivity leads to an increase in asthma symptoms or whether patients with asthma avoid physical activity. One prospective study on 2818 older women found an association between higher level of physical activity and lower risk of asthma exacerbations (16). To the author’s knowledge a comparable longitudinal study has not been conducted before evaluating the role of physical fitness and the development of respiratory symptoms. The present study aims to investigate the longitudinal
This article is protected by copyright. All rights reserved.
3
Accepted Article
association between physical fitness level and the development of asthma and asthma-like symptoms in a community based cohort of Danish schoolchildren.
Materials and Methods Subjects
The Odense schoolchild study is an ongoing prospective multidisciplinary study in a community based cohort of 1369 schoolchildren. The cohort has been followed since their third year of school in 1985-1986. Details of the selection criteria have previously been published (17). Parents gave
consent prior to the participation of their children in 1985 and informed consent was obtained at each follow-up. The study is approved by the local research ethics committee for Vejle and Funen County (Odense, Denmark) and the Danish Data surveillance Authority (Copenhagen, Denmark).
The following analysis is based on 1369 children at age 9 years (mean 9.7) and at follow-up from the 1369 eligible subjects: 1072 (78%) at age 15 (mean 15.6), 881 (64%) at age 20 (mean 20.3), and 814 (60%) at age 29 years (mean 29.3) who performed a satisfactory fitness test (figure 1). All data collection was performed from August through to June on each occasion. Cardio respiratory exercise test (fitness test)
The same protocol for the fitness test was used on all occasions (16). The test was a maximal progressive exercise on an electrically braked ergo meter cycle (Meditronic 40.-3, Kivex, Denmark at baseline and EM 840, Siemens, Denmark, at follow-ups). The work load was increased every 3 min with an incremental increase based on the subject's weight and exercise data from the
This article is protected by copyright. All rights reserved.
4
Accepted Article
questionnaire. The subjects exercised for approximately five 3-min periods and heart rates were measured continuously. Subjects were encouraged by the investigators to provide a maximal effort. The effort was accepted as maximal when the subject exceeded 85% of the predicted maximal heart rate, which was calculated as 220 - age in years. Failure to achieve 85% of the predicted maximum heart rate meant exclusion from further analysis. Maximum oxygen uptake (ml O2 x min-1 x kg-1) as
a marker of physical fitness was calculated from maximum mechanical power and weight (18). Lung function was measured in the upright position using a McDermott bellows spirometer (Garw Electronic Instruments, Penarth, Wales, U.K.) at age 9 and 15 years and a pneumotachograph (Vitalograph1 Compact; Vitalograph, Buckingham, UK) at age 20 and 29 years. The lung function test was at all ages done before the exercise test and accepted if the two highest values agreed within 5% according with at least 3 tests performed. Post exercise lung function tests was also done at age 9, 15 and age 21 but not reported in this paper. Non-smokers not diagnosed with asthma and not-reporting asthma-like symptoms served as the reference group for calculating reference values of Forced Expiratory Volume in one second (FEV1) and Forced Vital Capacity (FVC) which were derived from log-linear regression analysis with backward elimination entering sex, height and weight and age (19).
Questionnaire Asthma ever was defined by answering “yes” to one of these questions: At age 9 and 15 years: "Have you ever had asthma?" At age 20 and 29 years: "Is it your doctor’s opinion that you have asthma?" Defining asthma-like symptoms: Age 9 and 15: "Do you have wheeze and/or cough at rest?", "Do you have wheeze and/or cough when you are exercising?", "Do you feel shortness of breath at night?", "Do you feel shortness of breath in the morning?", "Do you have wheeze and/or
This article is protected by copyright. All rights reserved.
5
Accepted Article
cough in foggy weather?" and "Do you have bronchitis, i.e. periodic cough during several days/weeks?". Age 20 and 29: "Do you have attacks of breathing trouble with wheezing or whistling?", "Do you ever wake at night from shortness of breath?", "Do you ever wake at night from coughing?", "Do you have wheeze and/or cough when you are exercising?", "Do you have bronchitis, i.e. periodic cough which lasted more than 14 days?". Smoking was assessed by the following questions: At age 9 and 15 years: "Do you smoke?". At age 20 and 29 years: "Do you smoke?", "Have you ever smoked?"
Statistics
Continuous variables for groups are described by the mean with 95% confidence intervals of the mean (CI95). Dichotomous variables as percentages of the total group. Differences between groups were for continuous variables assessed by one-way ANOVA. Partial correlation coefficients for
physical fitness was calculated adjusted for sex. Differences for tests were considered statistically significant if P was 0.05 or less. To analyse longitudinal associations between physical fitness, asthma, and asthma like symptoms we used a multiple logistic regression using asthma and asthma like symptoms as the dependent variables and physical fitness as the main predictor. Analyses were adjusted for sex. Analyses were repeated including terms for sex, smoking, percent predicted FEV1 at age 9 and asthma at age 9 in the model. Statistical analysis was performed using the IBM Statistical Package for Social Sciences version 17 (PASW Statistics 17) (SPSS Inc., Chicago, IL, USA).
This article is protected by copyright. All rights reserved.
6
Accepted Article Results
1369 subjects completed the fitness test at age 9. Of these, 1202 (88%) were tested at least two times, 885 (64%) three times and 384 (28%) four times during the study. In correspondence 1225 (90 %) completed the questionnaire twice, 1047 (77%) three times and 559 (41%) four times. Demographic data were compared between those subjects who satisfactorily completed the tests and those who did not and no significant differences were found (data not shown). The prevalence of asthma and asthma like symptoms, and mean values of body mass index and fitness physical fitness at ages 9, 15, 20 and 29 years are shown in figure 2. The sex-adjusted partial correlation coefficients for physical fitness between measurements at age 9 and age 15, age 9 and age 20 and age 9 and age 29 years were r=0.339, r=0.331 and r=0.330 (all p
Title: Physical fitness and amount of asthma and asthma like symptoms from childhood to adulthood 1 Running head: Fitness, asthma and asthma like symptoms during three decades. Jørgen Guldberg–Møller1;
Bob Hancox2; Dennis Mikkelsen3; Henrik Steen Hansen3; Finn
Rasmussen§4
1.
Department of Respiratory Medicine, Roskilde Hospital, Denmark
2.
Department of Preventive & Social Medicine, Dunedin School of Medicine, University of
Otago, New Zealand.
3.
Department of Cardiology, Odense University Hospital, Sdr. Boulevard, 5000 Odense C;
Denmark
4.
Department of Allergy, Respiratory and Sleep Medicine, Near East University Hospital,
Yakin Dogu Bulvarı , Nicosia, Mersin 10, Turkey.
§ Address correspondence to: Finn Rasmussen, MD, PhD, DMSc; Department of Allergy and Respiratory Medicine, Near East University Hospital, Yakin Dogu Bulvarı; Nicosia, Mersin 10, Turkey. Tel: +90 392 675 1000; Fax: +90 392 223 6461, E-mail: [email protected] Keyword: physical activity, respiratory symptoms, asthma, longitudinal. Word Count: 2536
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/crj.12145
This article is protected by copyright. All rights reserved.
1
Accepted Article Abstract:
The potential benefits of physical activity on the development of respiratory symptoms are not well known.
Objective: The present study investigated the longitudinal association between physical fitness and the development of asthma-like symptoms from childhood to adulthood in a longitudinal community based study. Methods: Participants were assessed at ages 9, 15, 20, and 29 years. Asthma-like symptoms and physical fitness was assessed at each age. Results: Tracking for physical fitness was high from age 9 to 29 years. Using logistic regression,
high physical fitness at age 9 predicted a lower prevalence of asthma like symptoms at ages 9, 20, and 29 years. Asthma at age 9 and female sex and smoking at any age were also independently associated with the presence of asthma like symptoms. Our findings suggest that the risk for the development of asthma is reduced by 3% and of asthma-like symptoms reduced by 2% from early
adolescence to young adulthood (age 9 years to age 29 years) by increasing the maximal workload with 1 W.kg-1.
Conclusion: This finding provide further evidence of a possible beneficial effect of physical activity in childhood on the development of respiratory symptoms in adulthood and supports the notion that the lower levels of physical activity in recent decades may have contributed to an increase in the
prevalence of asthma and asthma like symptoms.
This article is protected by copyright. All rights reserved.
2
Accepted Article
Introduction It is evident that the prevalence of asthma has increased during recent decades (1-4) and there has been focus on whether this could be due to changes in lifestyle factors in westernised countries such as physical activity, allergen exposure, diet, and obesity. A growing body of evidence has shown an association between obesity and a higher prevalence of asthma (5, 6). Obesity is closely associated with low levels of physical activity and some studies (7) have suggested that physical inactivity is an independent risk factor for asthma apart from obesity. The evidence concerning the association between physical activity and asthma is sparse, but a recent review pointed out that the available
evidence indicates that physical activity is a possible protective factor against asthma development
(8). In the Odense Schoolchild Study we have previously shown an association between poor physical fitness in childhood and asthma development in young adulthood (9). Physical activity has been decreasing in westernised countries in the same time as the recent
increases in asthma prevalence have occurred so it is reasonable to ask if physical activity plays a role in preventing persistent asthma and asthma-like symptoms. Few cross-sectional studies are available, some of which have reported an association between higher levels of physical activity and a lower prevalence of asthma symptoms (10,11) whereas others have not (12-15). These studies differ in outcome measures and suffer the inherent problem of cross-sectional designs of being
unable to establish the temporal sequence: whether physical inactivity leads to an increase in asthma symptoms or whether patients with asthma avoid physical activity. One prospective study on 2818 older women found an association between higher level of physical activity and lower risk of asthma exacerbations (16). To the author’s knowledge a comparable longitudinal study has not been conducted before evaluating the role of physical fitness and the development of respiratory symptoms. The present study aims to investigate the longitudinal
This article is protected by copyright. All rights reserved.
3
Accepted Article
association between physical fitness level and the development of asthma and asthma-like symptoms in a community based cohort of Danish schoolchildren.
Materials and Methods Subjects
The Odense schoolchild study is an ongoing prospective multidisciplinary study in a community based cohort of 1369 schoolchildren. The cohort has been followed since their third year of school in 1985-1986. Details of the selection criteria have previously been published (17). Parents gave
consent prior to the participation of their children in 1985 and informed consent was obtained at each follow-up. The study is approved by the local research ethics committee for Vejle and Funen County (Odense, Denmark) and the Danish Data surveillance Authority (Copenhagen, Denmark).
The following analysis is based on 1369 children at age 9 years (mean 9.7) and at follow-up from the 1369 eligible subjects: 1072 (78%) at age 15 (mean 15.6), 881 (64%) at age 20 (mean 20.3), and 814 (60%) at age 29 years (mean 29.3) who performed a satisfactory fitness test (figure 1). All data collection was performed from August through to June on each occasion. Cardio respiratory exercise test (fitness test)
The same protocol for the fitness test was used on all occasions (16). The test was a maximal progressive exercise on an electrically braked ergo meter cycle (Meditronic 40.-3, Kivex, Denmark at baseline and EM 840, Siemens, Denmark, at follow-ups). The work load was increased every 3 min with an incremental increase based on the subject's weight and exercise data from the
This article is protected by copyright. All rights reserved.
4
Accepted Article
questionnaire. The subjects exercised for approximately five 3-min periods and heart rates were measured continuously. Subjects were encouraged by the investigators to provide a maximal effort. The effort was accepted as maximal when the subject exceeded 85% of the predicted maximal heart rate, which was calculated as 220 - age in years. Failure to achieve 85% of the predicted maximum heart rate meant exclusion from further analysis. Maximum oxygen uptake (ml O2 x min-1 x kg-1) as
a marker of physical fitness was calculated from maximum mechanical power and weight (18). Lung function was measured in the upright position using a McDermott bellows spirometer (Garw Electronic Instruments, Penarth, Wales, U.K.) at age 9 and 15 years and a pneumotachograph (Vitalograph1 Compact; Vitalograph, Buckingham, UK) at age 20 and 29 years. The lung function test was at all ages done before the exercise test and accepted if the two highest values agreed within 5% according with at least 3 tests performed. Post exercise lung function tests was also done at age 9, 15 and age 21 but not reported in this paper. Non-smokers not diagnosed with asthma and not-reporting asthma-like symptoms served as the reference group for calculating reference values of Forced Expiratory Volume in one second (FEV1) and Forced Vital Capacity (FVC) which were derived from log-linear regression analysis with backward elimination entering sex, height and weight and age (19).
Questionnaire Asthma ever was defined by answering “yes” to one of these questions: At age 9 and 15 years: "Have you ever had asthma?" At age 20 and 29 years: "Is it your doctor’s opinion that you have asthma?" Defining asthma-like symptoms: Age 9 and 15: "Do you have wheeze and/or cough at rest?", "Do you have wheeze and/or cough when you are exercising?", "Do you feel shortness of breath at night?", "Do you feel shortness of breath in the morning?", "Do you have wheeze and/or
This article is protected by copyright. All rights reserved.
5
Accepted Article
cough in foggy weather?" and "Do you have bronchitis, i.e. periodic cough during several days/weeks?". Age 20 and 29: "Do you have attacks of breathing trouble with wheezing or whistling?", "Do you ever wake at night from shortness of breath?", "Do you ever wake at night from coughing?", "Do you have wheeze and/or cough when you are exercising?", "Do you have bronchitis, i.e. periodic cough which lasted more than 14 days?". Smoking was assessed by the following questions: At age 9 and 15 years: "Do you smoke?". At age 20 and 29 years: "Do you smoke?", "Have you ever smoked?"
Statistics
Continuous variables for groups are described by the mean with 95% confidence intervals of the mean (CI95). Dichotomous variables as percentages of the total group. Differences between groups were for continuous variables assessed by one-way ANOVA. Partial correlation coefficients for
physical fitness was calculated adjusted for sex. Differences for tests were considered statistically significant if P was 0.05 or less. To analyse longitudinal associations between physical fitness, asthma, and asthma like symptoms we used a multiple logistic regression using asthma and asthma like symptoms as the dependent variables and physical fitness as the main predictor. Analyses were adjusted for sex. Analyses were repeated including terms for sex, smoking, percent predicted FEV1 at age 9 and asthma at age 9 in the model. Statistical analysis was performed using the IBM Statistical Package for Social Sciences version 17 (PASW Statistics 17) (SPSS Inc., Chicago, IL, USA).
This article is protected by copyright. All rights reserved.
6
Accepted Article Results
1369 subjects completed the fitness test at age 9. Of these, 1202 (88%) were tested at least two times, 885 (64%) three times and 384 (28%) four times during the study. In correspondence 1225 (90 %) completed the questionnaire twice, 1047 (77%) three times and 559 (41%) four times. Demographic data were compared between those subjects who satisfactorily completed the tests and those who did not and no significant differences were found (data not shown). The prevalence of asthma and asthma like symptoms, and mean values of body mass index and fitness physical fitness at ages 9, 15, 20 and 29 years are shown in figure 2. The sex-adjusted partial correlation coefficients for physical fitness between measurements at age 9 and age 15, age 9 and age 20 and age 9 and age 29 years were r=0.339, r=0.331 and r=0.330 (all p
