A Better Marker than BMI for BMD in African-American Women - Lab Report Example

Resting Energy Expenditure: A better marker than BMI for BMD in African American Women. Discussion: African American women tend to be more overweight and to have lower resting energy expenditures (REE) compared with Caucasian women. Weight is associated with bone mineral density (BMD), but the relation between BMD and REE has not been reported. In this study, the combined and independent contributions of age, body weight, body mass index (BMI), REE, physical activity, muscle strength, fat mass and lean body mass to lumbar spine, hip and total body BMC and BMD were assessed in four hundred postmenopausal African-American women aged 45-87 yrs, whose last menstrual period was at least 1 yr previous were enrolled from San Diego, CA who participated in this community based cross-sectional study.

The BMC and BMD in grams per unit projected area were measured at the lumbar spine, the hip (femoral neck, greater trochanter, intertrochanter), and the whole body using Hologic QDR-2000by a specially licensed and certified technician. Fat mass and lean body mass (LBM) were determined by dual energy x-ray absorptiometry (DXA). Weight and height were measured in subjects wearing light clothing without shoes. Weight was measured in kilograms and height was measured using a stadiometer. The validated Harris-Benedict equation was used to calculate REE.

A handheld grip dynamometer was used to assess grip strength. Three questions relating to frequency and intensity of exercise and participation in an organized exercise program were used to assess the physical activity of the participants. In addition each woman as asked to choose 1 of 11 statements which corresponded to PACE behavior scores, that best described her physical status. Information about cigarette smoking, post menopausal hormone therapy, diuretic use and current osteoporosis medication were also obtained using a standardized questionnaire.

All the statistical analysis was performed using SPSS version 11.0. From the results it was gleaned that the mean age was 61.6 yrs and the mean age at menopause was 43.1 yr. The mean BMI was 30.1 kg/m2. The mean LBM was 44.5 kg with a range of 29.8-65.6 kg. REE values ranged from 1008 to 2112 kcal/d, with a median of 1399 kcal/d and a mean of 1422.5 kcal/d. Dominant grip strength had a range of 8 – 46 kg, with a mean of 28.0 kg. Mean BMC at the lumbar spine and hip were 47.9 g and 29.0 g respectively.

Mean of total body BMC was 2513 g. Mean BMD at the lumbar spine and hip were 1.032 ns 0.901 g/cm2 respectively. Mean of total body BMD was 1.118 g/cm2. The mean PACE scores was 4.8. 39% of women had attended college, 15%were college graduates and 22% reported post graduate professional training. 56% were professionally employed and 37% were in nonprofessional careers. 4% of women never worked outside the home and 3%did not respond to this question. The Spearman correlation between REE and other variables with BMC and BMD at the lumbar spine, hip and total body was worked out.

The strongest correlation was found between REE and BMC or BMD. While age was inversely correlated to BMC and BMD , fat mass, LBM, weight BMI, waist and hip girth , REE and the dominant grip strength were all positively and significantly associated with BMC and BMD. A positive correlation was also observed between estrogen therapy and diuretic use with BMC and BMD. For the Spearman correlation between REE and the other variables a positive correlation was observed with fat mass, LBM, BMI and dominant grip strength.

Thus in the present study , REE was strongly correlated with BMC and BMD. The strong positive correlations between BMD, fat mass, LBM and REE confirm that body size and obesity protect against osteoporosis. The combined and independent positive associations between body size, mechanical loading and endogenous sex hormones support the biological plausibility that REE pays an important role in bone metabolism, which also supports the finding that REE is the best marker of BMD. The findings also support recent conclusions that lower activity- related energy expenditure rather than lower inherent REE may predispose African-American women to weight gain and obesity.

The PACE score results are compatible with the other studies that African-American women are less physically active than Caucasian women. How does the article relate to pharmacy practice in general? Health psychology is one of the areas of pharmacy practice. This article establishes the resting energy expenditure status of a cohort of African-American women. What is learned form the article? The results reflect the fact that African-American women are more overweight and less physically active than their Caucasian counterparts and it has also established a positive correlation between REE and BMC and BMD and that REE plays and important role in bone metabolism.

A fall in REE with menopause (Inverse relation between REE and age) has been attributed to the post menopausal loss of ovarian function compared with declines in muscle mass and physical activity. Thus differences in energy economy and physical activity have contributed to the higher rates of obesity in African-American women. Address the merits and limitations of the article? Merits: it has established that REE is the best marker for BMD. It has supported the evidence that African-American women have lower REE but are not more physically active then Caucasians and that this failure to compensate with lower energy intake, greater physical activity, or both may predispose African-American women to regain weight after weight loss.

Limitations: the study has concluded that REE plays an important role in bone metabolism, however the results in this study needs to be replicated and prospective studies are required to determine whether REE ia an independent risk factor for osteoporosis. Conclusion: From this study REE was found to be the best covariate of BMC and BMD in this cohort of African-American women.