Study design and participants
In this cross-sectional study, data from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) database were analyzed for the period 2008 to June 2011. The HCHS/SOL was a multisite community-based cohort study that examined the prevalence of chronic diseases and the associated health factors in a sample of Hispanic/Latino adults aged 18 to 74 years at baseline (2008–2011). The HCHS/SOL recruited 16,415 self-identified Hispanic/Latino people in four cities (Bronx, NY; Chicago, IL; Miami, FL; and San Diego, CA). Participants were recruited from randomly selected households. The detailed methods were reported previously . The institutional review boards at each site approved the study, and all procedures adhered to the Declaration of Helsinki. In this study, oversampled middle-aged and older adults (45–74 years) who reported having ABI scores from 2008 to 2011 were included. In addition, 2374 participants with missing data related to PA or who reported having comorbidities—such as heart diseases and respiratory disorders—were excluded. Therefore, the total primary analytical sample consisted of 15,031 participants.
Peripheral arterial disease (PAD)
The ABI is a noninvasive measure of PAD (arterial stenosis and stiffness) . The standard Doppler procedure using a Nicolet Doppler Elite 100R probe (Natus, Golden, CO) was used to measure the ABI, as described in previous studies . Low ABI values (≤0.9) were considered indicative of PAD and prognostic for atherosclerosis . Also, the classification of low ABI severity considered an index value between the ratio of 0.7 and 0.90 on either the left or right limb. A value between 0.7 and <0.4 was considered to indicate moderate to severe PAD, and all others were coded as normal.
Physical activity (PA):
The Global Physical Activity Questionnaire assesses the time spent in a typical week performing MVPA during work and leisure time, walking or biking for transportation, and being sedentary. Work-related, transportation-related, and leisure-time PA were included in our moderate PA variable. In the vigorous PA variable, only work-related and leisure-time PA were included. During a week, the MVPA and vigorous PA variables were created in accordance with the 2008 Physical Activity Guidelines for Americans. The PA recommendations for the general population, including people with PAD, were classified into three categories . The three categories for MVPA were as follows: (1) met the guidelines (≥150 min/week); (2) insufficiently active (>0 to <150 min/week); and (3) inactive (0 min/week).
The ABI is considered normal if its value is between 1.0 and 1.4, whereas values <1.0 or >1.4 are considered abnormal [4, 13]. In this study, the ABI was classified as normal or abnormal (mild, moderate, and severe). The sample was categorized as follows: normal ABI and physically active (combined MVPA >150 min), normal ABI but not physically active (combined MVPA <150 min), PAD and physically active (combined MVPA >150 min), and PAD but not physically active (combined MVPA <150 min).
Data analysis and statistical plan:
Baseline characteristics of the study population were compared across four different categories of combined PAD and PA: (1) normal ABI and physically active (combined MVPA >150 min), (2) normal ABI but not physically active (combined MVPA <150 min), (3) PAD and physically active (combined MVPA >150 min), and (4) PAD but not physically active (combined MVPA <150 min). The data were presented as means and standard deviations (M±SD) for normally distributed continuous variables, medians and interquartile range (MED [IQR]) for a non-normally distributed variables, and percentages for categorical variables. For categorical demographic characteristics, the Pearson chi-square test was performed to assess the differences in the four groups (PAD–non-PA, PAD–PA, healthy control and PA, and healthy control PA) and the two groups (PAD—mild and PAD—moderate to severe). In addition, the differences in continuous variables of demographic characteristics were assessed using the Kruskal–Wallis H test for the four groups and the Mann–Whitney U test for the two groups.
Generalized binary models were used to investigate the association between moderate PA as an independent variable (inactive, insufficient, and active) and PAD severity as a dependent variable after adjusting for age (years), sex, and education (less than high school and high school or more). Odd ratios were added in the calculation to explain the strength of the association between the dependent and independent variables. In addition, generalized linear models were used to investigate the association between the types of PA as independent variables (continuous values including work-related, transportation-related, recreational, total metabolic equivalents [METs], and total PA) and the severity of PAD as dependent variables. The models were adjusted using three controlling categories: the first model was used to control for age, sex, and education; the second model for the first model and smoking status, and body mass index (BMI); and the third model for all covariates with statins medication prescription.