Methods

The Multi-Ethnic Study of Atherosclerosis (MESA) is a longitudinal, population-based study of 6,814 men and women, initially free of clinical CVD, aged 45 to 84 years at baseline and recruited from 6 field centers: Baltimore, Maryland; Chicago, Illinois; Forsyth County, North Carolina; Los Angeles, California; New York, New York; and St. Paul, Minnesota. Specific racial/ethnic groups enrolled included non-Hispanic white/Caucasian, Black/African-American, Hispanic, and Chinese-American. Approximately, 50% of the participants enrolled were women. The baseline visit took place from July 2000 to September 2002. MESA was approved by institutional review boards at each site, and all participants gave written informed consent. The details of the MESA study design and recruitment strategy have been described in detail previously.

Information was obtained by questionnaire at the baseline examination in 2000 to 2002 regarding age, gender, race/ethnicity, medical history, and medication use. Current smoking was defined as having smoked in the past 30 days, whereas former smoker was defined as an individual who is not currently smoking but had smoked ≥100 cigarettes in his or her lifetime. Diabetes was defined as a fasting glucose ≥126 mg/dl or on hypoglycemic medication. Use of antihypertensive and other medications was based on clinic staff entry of prescribed medications. Resting blood pressure was measured 3 times in the seated position using a Dinamap model Pro 100 automated oscillometric sphygmomanometer (Critikon, Tampa, Florida), and the average of the second and third readings was recorded. Hypertension was defined as a systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or use of medications together with a self-reported diagnosis of high blood pressure. Total and high-density lipoprotein cholesterol and triglyceride levels were measured from blood samples obtained after a 12-hour fast. Low-density lipoprotein cholesterol was calculated with the Friedewald equation.

Psychosocial factors were assessed using standardized questionnaires which were available in English, Spanish, or Chinese. The presence of depressive symptoms was assessed by the Center for Epidemiologic Studies–Depression Scale (CES-D). Scores range from 0 to 60, with greater scores indicating higher levels of depressive symptoms. Scores were dichotomized into <16 and ≥16. Any depression was considered to be present if the CES-D score was ≥16, whereas participants with CES-D scores ≥27 were considered to have moderate–severe depression. Those who used antidepressant medication and were not previously designated as depressed by their CES-D score were also considered to have depression, and this was assessed by the standard MESA medication inventory.

Chronic burden was assessed using the chronic burden scale which measures ongoing difficulty in 5 life domains (personal health, health of a close contact, job, finances, and relationships) lasting more than 6 months. Scores range from 0 to 5 with greater scores reflecting greater degrees of chronic burden. Moderate chronic burden was defined as the presence of ≥3 life stressors lasting at least 6 months in duration.

Social support was assessed using the ENRICHD Social Support Inventory which consists of 6 questions pertaining to the availability of emotional support (scores range from 6 to 30; Cronbach α 0.87). Greater scores reflect greater availability of emotional support. A score of ≤12 was consistent with low levels of social support.

Race or ethnicity was characterized using participant responses to questions based on the 2000 US Census. Family annual income and education were obtained from the baseline MESA questionnaire and categorized using the following categories: for income, <$20,000, $20,000 to $49,000, and ≥ $50,000; and for education, less than high school, completed high school, technical school certificate or associate degree, and completed college or more.

Self-reported physical activity was obtained at baseline examination 1 using the MESA Typical Week Physical Activity Survey which assesses the time spent in and frequency of various physical activities over the past month. Metabolic equivalents were assigned to each physical activity, and the total Metabolic equivalent minutes per week of physical activity was determined for each participant. Additional categories of physical activity were created, including intentional physical activity which includes the sum of walking for exercise, sports, dancing, and other conditioning activities that are typically associated with physical activity guidelines. For analysis purposes, the log of intentional physical activity was used.

At the time of analysis, the cohort had been followed for incident CVD events for a median of 10 years. At intervals of 9 to 12 months, a telephone interviewer contacted each participant to inquire about interim hospital admissions, cardiovascular outpatient diagnoses, and deaths. Trained personnel abstracted medical records suggesting possible cardiovascular events. Two physicians independently classified the events and assigned incidence dates. If, after review and adjudication, disagreements persisted, a full mortality and morbidity review committee made the final classification. For the purposes of this study, we used all CVD events as the end point. Specifically, the end point included myocardial infarction, CHD death, resuscitated cardiac arrest, angina, stroke, stroke death, or other CVD death for total CVD events.

Baseline descriptive statistics were reported as means and standard deviations for continuous variables and frequencies and percentages for discrete variables. Unadjusted comparisons were tested using the chi-square test and one-way analysis of variance. Cox proportional hazard models for CVD events were used to estimate the hazard ratios (HRs) of the groups defined by psychosocial variables while adjusting for potential confounders. Model 1 adjusted for age, gender, and race. Model 2 further adjusted for education level, income level, smoking, systolic blood pressure, cholesterol (total and high density), diabetes, body mass index, and medication use (aspirin, statin, and antihypertensive). We also tested for 2-way interactions between categories of physical activity and depression, chronic burden, and social support, after fully adjusting as in model 2. The proportional hazards assumption was evaluated by testing Schoenfeld residuals. Statistical significance was set at a 2-sided p <0.05. Analyses were performed in Stata version 11.2 (StataCorp LP, College Station, Texas).

Results

A total of 6,795 subjects had complete data on physical activity at baseline (examination 1), thus comprising the study cohort for this analysis (mean age 62 years, 47% men). The prevalence of depression and/or antidepressant medication use was 18.4%, moderate or greater chronic burden 12.2%, and low social support 3.9%. Tables 1 and 2 show the characteristics of the study participants at MESA examination 1 according to the presence or absence of depression, chronic burden, and social support. Psychosocial factors were found to be negatively although weakly correlated with physical activity ( r = −0.046, p <0.001 for physical activity and any depression; r = −0.029, p = 0.017 for physical activity and chronic burden; r = −0.039, p = 0.001 for physical activity and low social support).

Stay updated, free articles. Join our Telegram channel

Join