Urban-rural differences in asthma prevalence among young people in Canada: the roles of health behaviors and obesity.

BACKGROUND Asthma prevalence has been reported to be lower in rural regions, but the reasons for this are not known. OBJECTIVE To confirm the existence of an urban-rural geographic gradient in asthma prevalence among Canadian youths and to evaluate whether this gradient was mediated by health behaviors. METHODS Cross-sectional data from 4,726 Canadian youth (grades 6-10) were collected during the 2001-02 Health Behaviour in School-Aged Children survey. Geographic region was categorized as metro (urbanized), non-metro but adjacent to metro, and rural. Asthma was defined via self-report of doctors' diagnoses and at least 1 of: (1) asthma symptoms or (2) a health care visit for asthma in the past year. Health behaviors (diet and physical activity) as well as obesity were also assessed. RESULTS Asthma prevalence was lowest in rural regions (metro = 17.7%, non-metro-adjacent = 15.6%, rural = 14.8%). A lower risk of asthma was associated with rural region (adjusted odds ratio [OR] = 0.76, 95% CI = 0.61-0.95) and living in non-metro-adjacent regions (adjusted OR = 0.81, 95% CI = 0.65-1.01). Health behaviors and obesity status did not mediate the association between geographic region and asthma. Being overweight or obese, having a high physical activity level, and exposure to passive smoking independently elevated the risk of asthma, whereas increased consumption of whole milk or vegetables were each protective. CONCLUSIONS Although asthma prevalence among youth was lower in rural areas, this association was not mediated by health behaviors or obesity. Other exposures, likely environmental, are the logical mechanisms through which rural geographic status is related to lower asthma prevalence.

[1]  P. Cullinan,et al.  Protective effect of fruits, vegetables and the Mediterranean diet on asthma and allergies among children in Crete , 2007, Thorax.

[2]  D. Cockcroft,et al.  Differences in respiratory symptoms and pulmonary function in children in 2 Saskatchewan communities. , 2004, Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology.

[3]  D. Nowak,et al.  Environmental exposure to endotoxin and its relation to asthma in school-age children. , 2002, The New England journal of medicine.

[4]  I. Janssen,et al.  Rural Canadian adolescents are more likely to be obese compared with urban adolescents. , 2008, International journal of pediatric obesity : IJPO : an official journal of the International Association for the Study of Obesity.

[5]  G. Weinmayr,et al.  Leisure time activity and new onset of wheezing during adolescence , 2007, European Respiratory Journal.

[6]  M. Jarvis,et al.  Factors determining exposure to passive smoking in young adults living at home: quantitative analysis using saliva cotinine concentrations. , 1991, International journal of epidemiology.

[7]  R. Plotnikoff,et al.  Physical activity, smoking, and obesity among Canadian school youth. Comparison between urban and rural schools. , 2004, Canadian journal of public health = Revue canadienne de sante publique.

[8]  D. Krewski,et al.  Increased effects of smoking and obesity on asthma among female Canadians: the National Population Health Survey, 1994-1995. , 1999, American journal of epidemiology.

[9]  C. Roberts,et al.  Validity of self-reported height and weight and predictors of bias in adolescents. , 2005, The Journal of adolescent health : official publication of the Society for Adolescent Medicine.

[10]  K. Berhane,et al.  Asthma in exercising children exposed to ozone: a cohort study , 2002, The Lancet.

[11]  D. Strachan,et al.  Parental smoking and childhood asthma: longitudinal and case-control studies , 1998 .

[12]  D. Strachan,et al.  Which aspects of the farming lifestyle explain the inverse association with childhood allergy? , 2006, The Journal of allergy and clinical immunology.

[13]  E. Rönmark,et al.  Agreement between parental and self‐completed questionnaires about asthma in teenagers , 2005, Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology.

[14]  D. Strachan,et al.  Worldwide time trends in the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and eczema in childhood: ISAAC Phases One and Three repeat multicountry cross-sectional surveys , 2006, The Lancet.

[15]  D. Strachan,et al.  Parental smoking and spirometric indices in children , 1998 .

[16]  D. Ownby.  Asthma in rural America. , 2005, Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology.

[17]  J. Stewart,et al.  Validity of Self-report Screening for Overweight and Obesity , 2008, Canadian journal of public health = Revue canadienne de sante publique.

[18]  H. Fonseca,et al.  Validity of BMI based on self‐reported weight and height in adolescents , 2009, Acta paediatrica.

[19]  M. Shields.  Overweight and obesity among children and youth. , 2006, Health reports.

[20]  Tara Vinodrai.  A Tale of Three Cities: The Dynamics of Manufacturing in Toronto, Montreal and Vancouver, 1976-1997 , 2001 .

[21]  N. Khardori.  Exposure to Environmental Microorganisms and Childhood Asthma , 2011 .

[22]  P. Nafstad,et al.  Physical activity affects the prevalence of reported wheeze , 2004, European Journal of Epidemiology.

[23]  D. Strachan,et al.  Parental smoking and prevalence of respiratory symptoms and asthma in school age children , 1998 .

[24]  Asher,et al.  The International Study of Asthma and Allergies in Childhood (ISAAC) , 1998, Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology.

[25]  Gabriele Nagel,et al.  Effect of diet on asthma and allergic sensitisation in the International Study on Allergies and Asthma in Childhood (ISAAC) Phase Two , 2010, Thorax.

[26]  L. Akinbami,et al.  Asthma prevalence, health care use, and mortality: United States, 2005-2009. , 2011, National health statistics reports.

[27]  D. Strachan,et al.  Health effects of passive smoking. 3. Parental smoking and prevalence of respiratory symptoms and asthma in school age children. , 1997, Thorax.

[28]  L. Williams,et al.  The Relationship of Physical Activity and Percentage of Body Fat to the Risk of Asthma in 8- to 10-year-old Children , 2007, The Journal of asthma : official journal of the Association for the Care of Asthma.

[29]  N. Pearce,et al.  Problems of measuring asthma prevalence , 1996, Respirology.

[30]  Setting Brazil.  Establishing a standard definition for child overweight and obesity worldwide: international survey. , 2008 .

[31]  R. Plotnikoff,et al.  Physical Activity, Smoking, and Obesity Among Canadian School Youth , 2004 .

[32]  N. Burioka,et al.  Clinical efficacy of the FLUTTER device for airway mucus clearance in patients with diffuse panbronchiolitis , 1998, Respirology.

[33]  D. Krewski,et al.  Obesity may increase the incidence of asthma in women but not in men: longitudinal observations from the Canadian National Population Health Surveys. , 2002, American journal of epidemiology.

[34]  J F Sallis,et al.  A physical activity screening measure for use with adolescents in primary care. , 2001, Archives of pediatrics & adolescent medicine.

[35]  K. E. Barron,et al.  Testing Moderator and Mediator Effects in Counseling Psychology Research. , 2004 .

[36]  W. Nystad.  The physical activity level in children with asthma based on a survey among 7–16‐year‐old school children , 1997, Scandinavian journal of medicine & science in sports.

[37]  Minna Kaila,et al.  Comparison of quality of life between asthmatic and healthy school children , 2005, Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology.

[38]  F. Leickly.  Persistence of Asthma Symptoms During Adolescence: Role of Obesity and Age at the Onset of Puberty , 2005, Pediatrics.

[39]  J. Lawson,et al.  Stabilization of an increasing trend in physician-diagnosed asthma prevalence in Saskatchewan, 1991 to 1998. , 2003, Chest.

[40]  S. N. Gabhainn,et al.  Health behaviour in school-aged children , 2000 .

[41]  Dennis Nowak,et al.  Exposure to farming in early life and development of asthma and allergy: a cross-sectional survey , 2001, The Lancet.

[42]  Shah Aa.  Worldwide variations in the prevalence of asthma symptoms: the International Study of Asthma and Allergies in Childhood (ISAAC) , 1998, The European respiratory journal.