Obesity and asthma: location, location, location

Abstract

There is a worldwide epidemic of obesity. In the USA, the prevalence of obesity, defined as a body mass index (BMI) ≥30 kg·m−2, has increased among adults aged 20–74 yrs from ∼15% in the late 1970s to ∼35% in 2010. Another third of the population is overweight (BMI ≥25 to <30 kg·m−2). The obesity epidemic has impacted both developed and developing nations throughout the world. The World Health Organization estimates that worldwide, ∼2 billion people are either obese or overweight. Obesity is a well-established risk factor for type 2 diabetes, hypertension and atherosclerosis. Obesity is also an important risk factor for asthma. In the late 1980s, two large surveys were published that examined the impact of obesity on the prevalence of chronic diseases [1, 2]. Both reported an increased prevalence of asthma in the obese and/or overweight. These studies received relatively little attention until ∼10 yrs later, when reports began to emerge describing associations between obesity and asthma in adults and children of multiple ethnicities throughout the world [3]. These association studies were limited by their inability to address the direction of causality and were initially interpreted as indicating a more sedentary lifestyle in asthmatics (due to respiratory symptoms during exercise) resulting in more obesity. It was not until publication of the first prospective analysis of the relationship between obesity and asthma in 1999 [4] that obesity really began to be appreciated as a major risk factor for asthma. The authors followed almost 86,000 initially nonasthmatic females over a 4-yr period. They observed that after adjustment for several factors, including exercise, initial BMI correlated strongly with the risk of new-onset asthma. Subsequently, several other prospective studies confirmed these …