MethodsThe IWHS cohort includes 41,836 women who, in January 1986, were randomly sampled from the Iowa State driver's list and responded to an initial questionnaire. This questionnaire queried numerous characteristics, including height to the nearest inch.As detailed previously [1], the IWHS data were linked to Centers for Medicare Services (CMS) enrollment and health care utilization data from 1986 through 2004. Medicare provides payment for all or part of health care for most US residents aged 65 and older [24], and data stemming from the payment of Medicare bills is now used widely as a population-based data source for clinical occurrences [24]. Of IWHS cohort members surviving to 65 years, 98% (40,377 of 40,997) met our CMS inclusion criteria and were therefore followed for incident VTE events [1].IWHS participants were considered to have had a VTE if any of the following VTE ICD-9 codes occurred on their Medicare MedPAR (hospitalization) discharge diagnosis records: 415.13, 451.13, 451.2, 451.81, 451.9, 453.0, 453.1, 453.2, 453.3, 453.43, 453.8, 453.9 [1]. Provoked VTE was classified on the basis of ICD codes indicating malignancy at the time of discharge, surgery in the three months prior to VTE diagnosis, hospitalization of 4 days or trauma in the two months prior to the VTE, or a serious medical disease at the time of hospital discharge. All remaining cases were classified as unprovoked [1].A recurrent event was defined as one that occurred subsequent to, but independently of, the incident event. We had no specific information about independence of events. Therefore, in order to distinguish index VTE events from recurrent VTE events, we required a 6-month lag period between the discharge date of the initial event and the admission date of the subsequent event [1].For this analysis of height and VTE recurrence, we included only women who experienced an incident event. Cox proportional hazards regression was used to evaluate the relation between height and VTE recurrence. As in our previous IWHS manuscript, which reported the association between height and risk of incident VTE