Eating disorders, menstrual dysfunction, weight change and DMPA use predict bone density change in college-aged women

INTRODUCTION

There are limited longitudinal studies that have evaluated bone mineral density (BMD) changes in college-aged women. Our objective was to simultaneously evaluate factors influencing 4-year BMD change.

METHODS

This was a longitudinal cohort study of healthy, physically active women in the US Military Academy (n=91; average age=18.4years). Assessments over four years included: height, weight, calcium intake, physical fitness, menstrual function (annual number cycles), oral contraceptives (OCs) or depot-medroxyprogesterone acetate (DMPA) use, and eating disorder behavior (Eating Disorder Inventory; (EDI)). BMD was measured annually at the lumbar spine and total hip by dual X-ray absorptiometry and calcaneal BMD by PIXI. Slope of 4year BMD change at each skeletal site (spine total hip and calcaneus) was calculated for each woman.

RESULTS

BMD gains occurred at the spine in 50% and the hip in 36% of women. In unadjusted analyses, spine bone gain was positively related to menstrual cycle frequency (p=0.04). Spine and hip BMD loss occurred in those using DMPA (p<0.01) and those with the highest EDI quartile scores (p<0.05). BMD change was unrelated to OC use. Hip and calcaneus BMD decreased with weight loss (average 4.8+2.2lb/year) as compared to those with stable weight/weight gain (p<0.05). In multivariable analysis, spine BMD increase was significantly related to African American (AA) race, normal EDI score and normal menses. Hip BMD increase was related to AA race, weight increase and normal menses. DMPA use was associated with spine, hip, and calcaneus bone loss.

CONCLUSION

On average, BMD may modestly increase in college-aged women, in the absence of risk factors. However, risk factors including subclinical eating disorders, weight loss, menstrual dysfunction and DMPA use can have significant detrimental effects on BMD in young healthy physically active women.

The influence of lifestyle, menstrual function and oral contraceptive use on bone mass and size in female military cadets

Purpose

To determine the influence of menstrual irregularity, oral contraceptive use and other factors on bone mineral density (BMD) and bone size at different skeletal sites in 135 college-aged fit women.

Methods

Menstrual history, oral contraceptive use, exercise history, and nutritional factors including calcium, caffeine, and alcohol intake as well as tobacco use were determined by written survey. Height, weight and fitness levels were measured. Spine and hip BMD were measured by dual x-ray absorptiometry (DXA), calcaneus BMD by peripheral DXA, and tibial bone mineral content (BMC) and size by peripheral Quantitative Computed Tomography (pQCT).

Results

The mean age was 18.4 ± 0.8 years. Weight and prior exercise were positively related to BMD at most skeletal sites and to tibial bone size. Milk intake was positively related to calcaneal BMD, tibial BMC and cortical thickness. Fracture history was an important predictor of spine, hip and heel BMD. Women who had ≥ 10 menstrual cycles in the year prior to BMD measurement had higher BMD at all sites as well as a greater tibial mineral content and cortical thickness than women who had oligomenorrhea/amenorrhea (≤ 9 cycles in the prior year; all p < 0.05). Oral Contraceptive (OC) users had significantly lower BMD in the spine (p < 0.02) and calcaneus (p = 0.04), smaller tibial periosteal circumference and lower tibial mineral content (p < 0.02) than non-OC users.

Conclusion

In a population of fit, college-aged women, OC use and oligomenorrhea were associated with reduced BMD and bone size. Weight, as well as prior exercise and milk intake was positively related to bone density and size at some skeletal sites. Understanding these relationships would help improve skeletal health in young women.

Determinants of bone mass and bone size in a large cohort of physically active young adult men

The determinants of bone mineral density (BMD) at multiple sites were examined in a fit college population. Subjects were 755 males (mean age = 18.7 years) entering the United States Military Academy. A questionnaire assessed exercise frequency and milk, caffeine, and alcohol consumption and tobacco use. Academy staff measured height, weight, and fitness. Calcaneal BMD was measured by peripheral dual-energy x-ray absorptiometry (pDXA). Peripheral-quantitative computed tomography (pQCT) was used to measure tibial mineral content, circumference and cortical thickness. Spine and hip BMD were measured by DXA in a subset (n = 159). Mean BMD at all sites was approximately one standard deviation above young normal (p < 0.05). African Americans had significantly higher hip, spine and heel BMD and greater tibial mineral content and cortical thickness than Caucasians and Asians. In Caucasians (n = 653), weight was a significant determinant of BMD at every skeletal site. Prior exercise levels and milk intake positively related to bone density and size, while caffeine had a negative impact. There was an apparent interaction between milk and exercise in BMD at the heel, spine, hip and tibial mineral content and cortical thickness. Our data confirm the importance of race, body size, milk intake and duration of weekly exercise as determinants of BMD and bone size.