Seasonal distribution of venous thromboembolism in Detroit as a function of potential risk factors.

For the venous thromboembolism (VTE) cases, the expected distribution against which the observed frequencies were tested was 25% per season. For the categorical potential risk factors, the expected distribution was that of the observed VTE cases. Categorical parameters are expressed as absolute values followed by the percentage in parentheses. Continuous variables are shown as medians followed by interquartile ranges in parentheses. The sample size for each category is shown in parentheses after the category label. Winter – December, January, February; spring – March, April, May; summer – June, July, August; autumn – September, October, November. Obesity was defined as a body mass index (BMI) >30 kg/m2.