Physical Activity Patterns Among US Adults With Asthma

Although the validity of these questions has not been tested directly, studies of the validity of similar physical activity instruments have suggested that the BRFSS questions should have reasonable validity.

Second, we calculated the proportions of participants who engaged in vigorous or moderate leisure-time physical activity using different definitions. On the basis of published formulas for estimated maximal cardiorespiratory capacity, a respondent was defined as being vigorously active if he or she participated in an activity with a metabolic equivalent (MET) level that > 60% of the calculated maximal cardiorespiratory capacity at least three times per week for > 20 min each time. MET values from published tables were assigned to activities. One MET is the energy expenditure of approximately 3.5 mL oxygen per kilogram of body weight per minute or 1 kcal/kg body weight per hour. Respondents who engaged in physical activity five times or more per week for at least 30 min on each occasion were designated as participating in moderate-intensity physical activity. Respondents who engaged in leisure-time physical activity that did not meet the criteria for moderate or vigorous physical activity were classified as being insufficiently active. Respondents who did not report engaging in leisure-time physical activity were classified as inactive.

Medicine News Blog by CanadianHealthCareMalll.Com – www.canadianhealthcaremallnews.blogspot.com

Third, we calculated energy expenditure (in kilocalories per week) for participants. Inactive participants were given a value of 0. For participants who reported participating in one or more physical activities or exercises, the weekly energy expenditure for each activity was calculated as follows: METs X hours per week X weight (in kilograms) and then summed.

We included the following covariates in our analyses: age; sex; race or ethnicity; educational attainment; and body mass index. Body mass index (in kilograms per square meter) was calculated from self-reported weights and heights.

Of the 367,381 people who were contacted, 184,450 participated in the survey. We excluded women who reported being pregnant (2,078 women; 1.1%) and respondents with missing values for asthma (2,536 respondents; 1.4%), age (1,109 respondents; 0.6%), race or ethnicity (1,927 respondents; 1.0%), educational status (471 respondents; 0.3%), physical activity level (2,059 respondents; 1.1%), and body mass index (10,229 respondents; 5.5%). After these exclusions, 165,123 participants (12,489 participants with current asthma, 4,892 participants with former asthma, and 147,742 participants who never had asthma) from the 50 states, the District of Columbia, and Puerto Rico were included in the analyses.

We calculated weighted percentages or means for the different measures of physical activity. We also calculated the mean weekly energy expenditure after capping the calculated energy expenditure of some participants at 8,000 kcal per week (representing about 10 h of vigorous activity per day).