As part of the Cardiovascular Health Study (CHS), DXA scans were preformed on 1,591 older men and women, including 302 African Americans. CHS is a longitudinal, population-based cohort study of men and women over the age of 64 recruited from four geographically distinct sites in the United States. Additionally, other medical, functional and psychosocial data were gathered on these individuals. A more complete description of the CHS is provided elsewhere. Two sites, Pittsburgh, PA and Sacramento, CA, obtained DXA during 1995-1996, using a protocol similar to that used in the Study of Osteoporotic Fractures and the Fracture Intervention Trial. Scans were acquired using the medium array mode on Hologic QDR-2000 densitometers (Hologic Inc., Waltham, MA) and read by individuals blinded to other information about the participants at the University of California, San Francisco Reading Center using Hologic software version 7.10. The coefficient of variation for hip BMD measurements was <0.75%.
In an exploratory fashion, we examined the relationship of BMD in African-American participants to variables which have been associated with decreased BMD in prior studies of white women and which were collected by the CHS. We hypothesized that, among older African Americans, we would observe relationships similar to those found in whites. BMD was measured for total body, total hip and AP views of the Li to L4 subregion of the lumbar spine. cheap antibiotics
After testing for the effect of gender on BMD, we conducted the remainder of the analyses using gender-stratified samples. All statistical analyses were performed with SPSS versions 10 and 12. The following variables: age, gender, education, income group, activities of daily living score (ADL), instrumental activities of daily living score (IADL), drinks per week, depression score, self-reported health, pack years smoked, weight, height, body mass index (BMI), Kcals of physical activity, calcium supplement use, hydrochlorothiazide use, oral steroid use, oral estrogen use and current smoking were tested for univariate associations with BMD at the three sites. Associations of continuous variables were tested with the Pearson correlation coefficient and associations of dichotomous variables were evaluated with the Student’s t-test. In Step 2, variables that showed a univariate association with BMD at p<0.1 were entered into backwards elimination linear regression models for each DXA site. Because of the exploratory nature of this analysis, the models were intentionally built to err on the side of entry (p=0.1 to enter, p=0.2 to remove). Variables which emerged as independent correlates were then forced into a final linear regression model for each BMD site in order to maximize the number of subjects included in the final model. The percent contribution of each variable to the variability in BMD at each site was estimated by deriving the R2.
The following variable definitions were used: Age refers to the age in years at the time of the BMD determination. Kilocalories (kcal) were derived algo-rithmically using the validated physical activity questionnaire from the Minnesota Heart Survey and represent kcals above the estimated basal metabolic rate. ADL and IADL were recorded on five- and six-point scales, respectively. Lower scores correspond to greater functional independence. A 10-item version of the Center for Epidemiological Studies Depression Scale (CES-D) was used to screen for depression. The cut-off score for depression in the 10-item version (CES-Dm) is >10. The CES-Dm has demonstrated validity as a screening tool for depression in older adults. Self-rated health was measured on a five-point scale (5=excellent, 4=very good, 3=good, 2=fair, l=poor). Combined family income information was collected and is reported in eight categories (1=<$5,000, 2=$5,000-$7,999, 3=$8,000-$ 11,999, 4=$12,000-$15,999, 5=$16,000-$24,999, 6=$25,000-$24,999,1= $25,000-$49,000, and 8=>$50,000).
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