Question

Asthma is a chronic lung disease caused by inflammation of the lower airways and episodes of airflow obstruction. Asthma episodes or attacks can vary from mild to life-threatening. In 2007, about 7% percent of the U.S. population was diagnosed with asthma and there have been a growing number of new cases since that time. There are several known risk factors identified as triggers of asthma symptoms and episodes, including inhalation of allergens or pollutants, infection, cold air, vigorous exercise, and emotional upsets. There is also growing evidence relating body-mass index to asthma in both children and adults. Design a study to investigate whether there is such an association.

Choose a study design and justify the reasons you chose the design over others.

Select a statistical measure you would use to describe the association (if there is one) between body mass index and asthma.

In addition, address:

Subject selection

Issues relating to the measurement of both the exposure and the outcome

Potential biases that the study might be prone to, and how they might be handled

Possible confounding factors and effect modifiers and how to overcome their effect

Answer 1

Obesity and Asthma having link..Few studies investigated the relationship between childhood obesity and asthma symptoms.Studies have some limitations because it is hospital-based ,case-control and small sample size..
Study design:
      Total number of elementary school(6,279schools) from each residential area random sampling method was used..Residential area include metropolitian provincial,rural and industrial area..Age group 8-11 year old was randomly selected..informed consent,letter invitation obtained from parents and caregivers..Total 50,200particpants in that 427 elementary schools..
statistical measure:
   BMI was calculated by self-reported height,weight and calssified into four groups(<25 percentile, 26 -50 percentile, 51 -75 percentile and >75 percentile) BMI for age percentile korean growth chart developed based on data surveys for children and adolescents..we evaluated environmental factor and wheeze using two-stage hierarchical model because contextual effect of residential area on the risk of wheeze..First analysis conducted to investigate any independent association between wheeze in residential area..second analysis multilevel regrssion using the GLIMMIX procedure..These analysis conducted seperately by gender.
Discussion:
   Using this two model BMI percentage are high and it was more in girls especially for korean children..lowest birth weight and BMI showing less wheezing..poor living environment like ETS exposure,pets at home,moisure associated with more for wheezing both boys and girls in multilevel logistic regression analysis..Non -response bias might have occured due to a low response rate..To acquire an unbiased estimate of risk ratio further investigation needed..Further studies need more detailed on the symptoms of asthma and potential confounding factors like socioeconomic status,residential areas and indoor or outdoor environment also should be considered..
   so more than limitations,we need prevention strategy and implementation plan to reduce asthma and symptoms should be considered in residential area..