Is There a Link between Obesity and Asthma in Adolescent Children - Literature review Example

Is there a link between Obesity and Asthma in Adolescent Children? In this literature review, a computer search in the PubMed electronic database was used to identify sources on the relationship between obesity and asthma using keywords “obesity”, “asthma” and “adolescence” as well as combined keyword searches “obese asthma”, “obese adolescent” and “adolescent asthma”. A combination of cross-sectional, case-control and prospective original articles and meta-analyses published from January 2005 to January 2014 have been reviewed. The increased prevalence of obesity and asthma in the last two decades has provoked the widespread scholarly interest in the relationship between obesity and asthma. A vast majority of the sources reviewed suggest the existence of a causative relationship between obesity and asthma, but there is no consensus on the pathophysiological mechanism involved yet. Studies consistently show that obesity is increasingly becoming a crisis among children and adolescents and it potentially heightens the risk of asthma; similarly, the impact of obesity on asthma is generally modest and depends on variables such as age and sex. Search Criteria In this literature review, a computerized search in the systematic review based indexed database PubMed electronic database was conducted using the keywords “obesity”, “asthma” and “adolescence”. Combined keyword searches such as “obese asthma”, “obese adolescent” and “adolescent asthma” was also used to identify the appropriate literature in the field. Given the vastness of resources yielded by the keyword searches, the literature used in the review was deliberately selected through a restrictive inclusion criteria based on relevance to topic, year of publication, subject and cohort age. This review limited itself to cross-sectional, case-control and prospective original articles and meta-analyses published from January 2005 to January 2014. These were both primary and secondary sources of information, including study reports by original researchers and review article descriptions of studies by other persons other than the original researchers. Articles that were published more than ten years ago, that is 2005 and below, as well as articles that were not concerned with the relationship between obesity and asthma were excluded from the list. The type of literature source considered were journals because they are up-to date than books, which despite being acceptable and valuable sources of information, tend to be dated due to the time it takes for them to be published. Introduction There is an unprecedented upsurge in the global obesity epidemic presently, with nearly 300 million adults categorized as obese today; obesity is also increasingly becoming a crisis among children, with nearly 22 million children under five years of age being overweight in the U.S. alone1. Obesity is increasingly becoming prevalent in childhood and adolescence, particularly due to the excessive access to conveniences in modern societies, sedentary lifestyles and physical inactivity2. While the number of obese children has almost doubled since 1980, the number of obese adolescents in the US has nearly tripled in the same period; correspondingly, asthma prevalence rates have also increased in the same fashion. Precisely, asthma prevalence rates are nearly 2.5 times higher presently than they were 20 years ago; the prevalence of bronchial asthma has been on an upwards trend from the 1960s. Statistically, nearly a 3.6% to 5.8% increase in the prevalence of asthma was reported in the North American children in the year 20033; this has led to the current interest in the relationship between asthma and obesity. It is was not clear whether the association between obesity and asthma was causal or merely coincidental, but more recent literature posits some breakthroughs in the investigations. Obesity does negatively impact many organ systems in the human body, including the respiratory system4; it is widely believed that obesity is the single most causal factor of lung diseases. Existing data has consistently suggested that obesity plays a great role in aggravating the risk of developing new cases of both objectively as well as rigorously defined asthma. According to Guibas et al5, the obesity/ asthma link among adults is clear today, but there is no consensus yet on the nature of such a link when it comes to children; this has partly been attributed to the fact that Body Mass Index (BMI) is not an effective surrogate fat mass marker in childhood. Whereas obesity in adults is clearly defined as BMI ≥30 kg/m2, this cut-off point cannot be used as a correct measure of adiposity in children because BMI keeps changing with age6. In that respect, the manner in which obesity affects the asthma phenotype in children and adolescents largely remains unclear up to date. Asthma and obesity are presently listed as the major causes of morbidity in childhood and adolescence; early obesity exposes children to higher risks of chronic degenerative diseases in their later lives. The prevalence of both asthma and obesity in the same period has motivated the present literature review on the issue of whether obesity could represent a risk for the emergence of asthma in adolescents. Previous studies have generally focused on the investigation of whether the increased preponderance of obesity and asthma are related. The present review delves into the study of the existing literature on the nature of the relationship between obesity and asthma with a primary focus on whether obesity is linked to the development of asthma in adolescents. Obesity and Asthma Links Asthma is accountable for nearly a quarter million mortalities and about 15 million disability-adjusted life years every year, and it is the most pervasive chronic noninfectious childhood disease that affects nearly 300 million people around the world today7. There is no standard definition of asthma but it is generally understood as a complex group of conditions and an allergic disease, though a vast majority of asthmatic children do not have any known allergies; similarly, the causes of asthma are not well understood and there seems to be no consensus yet on the relative contribution of different putative risk factors. Cross-sectional studies have established a steady rise in the prevalence of asthma in the obese patients’ population group while numerous prospective studies have established that there indeed exists a positive correlation between baseline BMI and the consequent development of asthma8. Prospective studies and studies in the pediatric populations find that whereas obese people are at a higher risk of developing asthma, the effects are even much pronounced in the female than in the male gender. Obesity effects in terms of the risk of asthma development are much pronounced in adolescent girls than in boys because girls often arrive at the age of maximum lung growth faster and earlier than boys9. In that case, it is evident that obesity potentially heightens the risk of asthma, only that the impact is generally modest and depends on variables such as age and sex; increased obesity heightens the severity of asthma, thus, the more the weight gain the higher the risk of development of asthma10. Weight loss has been noted to lead to improved outcomes with regards to asthmatic symptoms and treatment; generally, based on the existing evidence so far, key observations can be made about the relationship between obesity and asthma. Shore11 demonstrates that obesity precedes asthma, greater obesity results to a correspondingly greater effect on asthma, and that obesity is linked to intermediate asthma phenotypes; obesity increases not only the prevalence, but also the incidence and severity of asthma and weight loss corresponds to significant asthma outcomes. In that respect, there is no doubt that a causal relationship can be inferred between obesity and asthma; the biological explanation for the association between obesity and asthma is complex though12. Obesity and Asthma in Adolescents Obesity in childhood and adolescence has raised great concerns in clinical practice, thereby provoking focus on the potential physical as well as psychological impacts of childhood and adolescent obesity13. Presently, nearly 1 out of 7 adolescents in the U.S. are obese; generally, adolescent obesity has been attributed to poor health outcomes and poor physical quality of life. Asthma and obesity among the American youth have raised great health concerns because they affect a huge chunk of the adolescent population; the prevalence, morbidity as well as mortality rates of asthma are particularly high among American adolescents. The number of adolescents of 12 to 19 years of age with obesity in America went up from 1 in every 20 adolescents in the late 1970s to about 1 in every 6 adolescents in the year 2008. Despite that excess fat or simple obesity and asthma are growing health concerns throughout the world today, the association between asthma and obesity in children is not so clear14; previous studies have suggested a link between asthma and obesity in adolescents. Generally, adolescents from poor households are more likely to be obese and asthmatic concurrently; earlier studies suggested that it is the reduced physical inactivity due to asthma that contributed to increased obesity prevalence among the adolescents but a vast majority of prospective studies have found that obesity usually precedes asthma. Many weight loss studies have supported this assertion because they have clearly shown that asthmatic obese patients often present with significant outcomes in asthma morbidity after losing weight15. For instance, restrictive, very low-energy foods have been found to yield effective results as far as enhancing asthma outcomes in asthma patients is concerned; nonetheless, concerns over the potential negative impact of restrictive diets on growth have been raised with respect to their use on adolescents16. Obesity is arguably a great risk factor for impaired lung functioning and an inhibitor of long-term survival in adolescents; untreated asthma is more likely to degenerate to irreversible obstruction of the airway. It is evident that the heightened risk of asthma in obese adolescents has been suggested in many studies, but so far there is scanty evidence of the underlying relationship between obesity and asthma17. There is increasing awareness of the correspondence between numerous aspects in the pathophysiology of asthma and obesity and the relationship between increased body mass index and elevated asthma incidence rates18. The link between increasing body mass and asthma in adolescents varies by race or ethnicity; precisely, extreme obesity has largely been attributed to the prevalence of asthma in Asian/Pacific Islander as well as the non-Hispanic white adolescent population groups. A vast deal of epidemiological evidence suggests that obesity is the single most significant predictor of the likelihood of incident asthma19. According to recent data, even a modest level of weight gain potentially increases the risk of asthma, and obese asthmatic patients do represent a special phenotype of asthma. In establishing the case factors of a disease, it is important to distinguish between atopic and non-atopic diseases because each one of them have different causal mechanisms20. Whereas atopy is the single most influential host factor in the development of asthma, many studies have consistently established a link between obesity and the increased likelihood of the development of atopy21. Conventionally, asthma is defined by TH type 2 (Th2)-mediated allergic inflammation, but obese asthma patients are more likely to present with heightened asthma severity predicated by the worsened exacerbations as well as the decreased asthma control. In that respect, there is mounting evidence that suggests that obesity does not cause asthma through the traditional Th type 2-mediated inflammatory mechanism. The fact that obese asthma patients react to conventional asthma therapies in diverse ways is a potential indicator of the existence of a distinct phenotype of asthma. Despite that asthma is attributable to airway inflammation and reversible obstruction of the airflow, obese asthma patients do not present with any symptoms of heightened airway inflammation; this most likely suggests the presence of a non-Th2 cytokine-driven as well as non-allergic asthma phenotype22. The severity of obesity is also greatly correlated with exacerbated asthma-related utilization of healthcare as well as asthma-related treatment, consequently prompting the upsurge in medical emergencies among adolescents with asthma in the United States and across the world. The mechanism of obesity and development of asthma in adults is well established; it is widely understood that obesity in adults results to chest restriction and reduced functional residual capacity as well as expiratory reserve capacity while undermining maximum lung capacity23. There is little evidence of research on the pulmonary mechanics in children and adolescents, and a vast proportion of inconsistencies exist in the present sources. There is sufficient evidence to suggest that the association between obesity and lung outcomes varies significantly depending on other factors other than age and gender such as activity level, as well as the age of onset of obesity. The impact of obesity on lung function in adolescents is thought to be similar to the observed effects in adults because obese adolescents that are generally healthy usually have reduced residual volumes and functional residual capacities that vary proportionately depending on the severity of chest restriction and impaired diffusion capacity. Discussion It is evident that there has been an unprecedented increase in the incidence of both obesity and asthma in the world, and particularly in the United States, thereby fuelling speculations over the relationship between obesity and asthma. A vast majority of the sources reviewed suggest the existence of a causative relationship between obesity and asthma, but there is no consensus on the pathophysiological mechanism involved yet. The present literature review reveals that the current data is ridden with inconsistencies and hypotheses that are yet to be validated; there is great need for more knowledgeable research to inform current practice on the exact relationship between obesity and asthma. What is known so far is that asthma is a multifactorial disease that is arises from a unique interaction between environmental and genetic factors; positive family history is a significant predictor of the likelihood of asthma in future since genes play a great role in determining development of the disease. Nonetheless, childhood obesity is more likely to exacerbate asthma severity and asthma control in adolescents; the prevalence of obesity in the asthma patient group is greater compared to the non-asthmatic patient group24. Furthermore, the asthma obese patients are common encounters in clinical practice today than ever before, a phenomenon that raises great concerns regarding the possible causative links between obesity and asthma. The notion that severe obese adolescents with asthma are the greatest consumers of healthcare services, including ambulatory and emergency room admissions, is a common theme in the literature reviewed25. Obese adolescents are more likely to have frequent and severe asthma symptoms than any other group, are more likely to receive more asthma medication prescriptions, have poor lung function outcomes, and are more likely to be booked into emergency services and hospitals. Childhood obesity has been reported mostly among the ethnic minorities and in most of those cases, it is comorbid with asthma26; the relationship of obesity and asthma is definitely not bi-directional as previously thought because studies have consistently indicated that obesity precedes and potentially worsens asthma. Nonetheless, the causal link between obesity and asthma is so weak in many studies, partly due to the great variability in asthma control as well as morbidity; some studies limit the variability in asthma morbidity while others do not. While studies that utilize a cohort of limited variability in asthma severity fail to establish a causal link between asthma and obesity, those that allow great variability in asthma severity do find a causal link between asthma and obesity27. Nonetheless, the lack of certainty on the causal relationship between obesity and asthma notwithstanding, there is great need for knowledge of the obese-asthma phenomenon, to alleviate the great symptom burden as well as morbidity suffered by this group of patients. Conclusion The present literature review reveals there has been a massive scholarly interest in the relationship between obesity and asthma, partly due to the unprecedented increase in the prevalence and incidence of the two diseases in the same period, from the 1980s up to date. Some studies show that obesity is increasingly becoming a crisis among children and adolescents and that it potentially heightens the risk of asthma; other studies find that the impact is generally modest and depends on variables such as age and sex. While some of the sources reviewed fail to establish a strong connection between obesity and asthma, others propose a causative relationship between them, even though the mechanism of this process is not so clear yet. Most sources agree that obese asthma patients are more likely to present with heightened asthma severity predicated by the worsened exacerbations as well as the decreased asthma control. Bibliography Guibas et al., “The obesity-asthma link in different ages and the role of body mass index in its investigation: findings from the Genesis and Healthy Growth Studies. Allergy, 68 no. 10 (2013):1298-305. Sin, D.D. & Sutherlant, E.R. Obesity and the lung: 4 . Obesity and asthma. Thorax, 63 (2008):1018–1023. Castro-Rodriguez, José.A., “Relationship Between Obesity and Asthma,” Arch Bronconeumol, 43 no. 3 (2007):171-5. Story, R.E., “Asthma and obesity in children, Curr Opin Pediatr 19 (2007): 680–684. Shore, S.A., “Obesity and asthma: Implications for treatment,” Curr Opin Pulm Med, 13 no. 1 (2007): 56-62. Claude & Salome, “Asthma and obesity: A known association but Unknown mechanism,” Respirology, 17 (2012): 412–421. Swallen et al., “Overweight, Obesity, and Health-Related Quality of Life Among Adolescents: The National Longitudinal Study of Adolescent Health. Pediatrics, 115 no. 2 (2005): pp. 340 -347. Jay et al., “The Relationship between Asthma and Obesity in Urban Early Adolescents,” Pediatr Allergy Immunol Pulmonol, 25 no. 3 (2012): 159–167. Black, M.H. et al., “Higher Prevalence of Obesity Among Children With Asthma,” Obesity, 20 no. 5 (2012): 1041–1047. Delgado, J., Barranco P., & Quirce, S., “Obesity and Asthma,” J Investig Allergol Clin Immunol, 18 no. 6 (2008): 420-425. Lugongo, Kraft & Dixon, “Does obesity produce a distinct asthma phenotype? J Appl Physiol, 108 no. 3 (2010): 729–734. Strina A. et al., “Risk factors for non-atopic asthma/wheeze in children and adolescents: a systematic review,” Emerging Themes in Epidemiology, 11 no. 5 (2014): 1-11. Luna-Pech, J.A. et al., “Normocaloric Diet Improves Asthma-Related Quality of Life in Obese Pubertal Adolescents,” Int Arch Allergy Immunol 163 (2014):252–258. Lang, J.E., “Exercise, obesity, and asthma in children and adolescents,” J Pediatr, 90 no. 3 (2014):215-217. Jay, M., “Accuracy of Weight Perception among Urban Early Adolescents with Uncontrolled Asthma and Their Caregivers,” Ann Behav Med. 45 no. 2 (2013): 239–248. Ali & Ulrik “Obesity and asthma: A coincidence or a causal relationship? A systematic review,” Respiratory Medicine, 107 no.9 (2013): 1287-300.  Read More