Association of selected lifestyle factors with BMD

1
Lifestyle Factors Associated with Bone Mineral
Density in Adolescent Women Delia Scholes1,2,
Andrea Z. LaCroix1,2 , Laura E. Ichikawa1, Susan
M. Ott2, William E. Barlow1,2 1Group Health
Cooperative and the 2University of Washington,
Seattle WA
INTRODUCTION
RESULTS

• Background
• Maximizing peak bone mass is essential for
  prevention of future morbidity from osteoporosis.
  
• Adolescence is a particularly critical time for
  bone mass accrual. More than half of peak bone
  mass is attained during adolescence and, for many
  anatomic sites, bone mass accrual is virtually
  complete by age 18.
• Heritable factors are most important in peak bone
  mass attainment. But identification of
  modifiable risk factors offers opportunities for
  interventions aimed at improving bone health.
• A number of lifestyle factors, including dietary
  factors, smoking, and exercise, have been both
  positively and negatively associated with bone
  density.
• Purpose
• To evaluate the association between selected
  lifestyle factors and bone mineral density in a
  population-based study group of adolescent women.

Selected Baseline Characteristics
Association of selected lifestyle factors with
BMD Adjusted mean BMD
N Hip Spine Whole Body __________________
________________________________________________
Current Yes 39 0.935 0.969 1.069 smoker No 1
35 0.968 0.987 1.088
(p0.12) (p0.40)
(p0.30) Wt-bearing 0-lt55 62 0.947 0.965 1.069
activity 55-lt70 62 0.962 0.997 1.086 70 5
0 0.976 0.986 1.099 (p0.39)
(p0.26) (p0.26) Dietary
0-lt650 60 0.944 0.972 1.072 Calcium 650-lt1300 5
3 0.971 0.986 1.071 (mg/day) 1300 52 0.970 0.
992 1.109 (p0.30)
(p0.58) (p0.06) Dietary 0-lt45 4
4 0.953 0.960 1.087 Protein 45-lt90 90 0.951 0
.976 1.078 (gm/day) 90 31 0.999 1.035 1.095
(p0.26) (p0.15)
(p0.70) Dietary 0-lt180 59 0.958 0.96
2 1.066 Magnesium 180-lt360 83 0.952 0.976 1.07
2 (mg/day) 360 23 0.999 1.058 1.169
(p0.29) (p0.04)
(p0.002) Any caffeine Yes 104 0.952 0.981 1.0
80 intake No 70 0.973 0.986 1.089
(p0.20) (p0.77)
(p0.58) Caff. cola 0-1 123 0.969 0.985 1.095
(drinks/day) 2 50 0.938 0.978 1.053
(p0.12) (p0.72)
(p0.01) Alcohol 0 74 0.954 0.978 1.078 (d
rinks/mo) lt5 62 0.969 0.996 1.098 5 38 0.96
0 0.970 1.072 (p0.71)
(p0.44) (p0.31) _____________
__________________________________________________
__________ Adjusted for the following
baseline covariates age, height, weight, and
calcium as continuous variables ethnicity,
number of periods in last year and hormone-based
contraception as categorical variables.
Correlation between selected variables Wt.
bearing Calcium Protein Magnesium Caff.
Cola Alcohol activity _______________________
__________________________________________________
______ Wt bearing activity 0.24
0.27 0.28 -0.23 -0.09 Calcium
0.87 0.87 -0.14
0.02 Protein 0.88
-0.11 -0.002 Magnesium -0.20
0.005 Caff. Cola 0.18 ________________
__________________________________________________
_____________ Age -0.09 -0.05 -0.01
0.03 0.11 0.22 BMI -0.05 -0.07
-0.09 -0.09 0.14 0.07 _____________________
__________________________________________________
________ plt 0.05
Age 16-18 (vs. 14-15)
Non-white
BMI lt18.5 (vs. normal)
BMI 25-lt30 (vs. normal)
BMI 30 (vs. normal)
0-7 periods (vs. 8)
Ever pregnant
Personal fracture
Hormonal contraception
Magnesium 180-lt360 mg/day (vs. lt180)
Magnesium 360 mg/day (vs. lt180)
Calcium 650- lt1300 mg/day (vs. lt650)
Calcium 1300 mg/day (vs. lt650)
METHODS
Wt. bearing activity score 55-lt70 (vs. lt55)
Wt. Bearing activity score 70 (vs. lt55)
Study Setting Group Health Cooperative (GHC), a
mixed-model HMO located in Washington
state Study Design Cross-sectional Participan
ts 174 adolescent women, ages 14-18
years Selected using computerized databases
from this health plan Inclusion/ Not
pregnant or lactating, post-menarche, no
Exclusion conditions or medications that might
affect bone density, informed consent from
parents for participants lt18 Data
Collection Health questionnaire Food frequency
questionnaire Exam DEXA Lifestyle
Factors Current smoking weight-bearing physical
activity dietary intake of magnesium,
calcium, protein, alcohol, caffeine and
caffeinated cola beverages Outcome Hip,
spine, and whole body bone mineral density
(g/cm2) using DEXA Analyses Associatio
n of lifestyle factors with BMD, after
adjustment for the effects of age, height,
weight, ethnicity, number of periods in the
past year, hormonal contraception, and
dietary calcium All study procedures were
reviewed and approved by the GHC Human Subjects
Committee

• Summary of Results
• A number of biologic and lifestyle variables were
  associated with bone density as the hip or other
  anatomic site.
• However, after adjusting for other factors known
  to affect bone density, the majority of the
  lifestyle factors we examined were not
  significantly associated with BMD in these
  adolescents.
• Two dietary factors, magnesium and caffeinated
  cola consumption, were significantly associated
  with BMD in this study group
• Dietary intake of magnesium was positively
  associated with BMD at two anatomic sites, the
  spine and whole body.
• Consumption of caffeinated cola beverages was
  negatively associated with whole body BMD.

Smoker
lt5 alcoholic drinks/mo (vs. 0)
5 alcoholic drinks/mo (vs. 0)
2 caff. cola drinks/day (vs. 0-1)
mean
s.e. median HIP BMD Spearman
correlation Age at menarche (yrs.) 12.3
0.1 12.0 0.05 Height (in) 64.1
0.2 64.1 0.29 Weight (lb)
142.4 2.2 137.1 0.42 Weight-bearing
activity 61 1 61 0.25 Calcium
(mg/day) 973 47 833 0.11 Protein
(gm/day) 66 3 59 0.09 Magnesium
(mg/day) 235 9 220 0.09 Caffeine
(mg/day) 52 6 20
-0.10 Calories (kcal)
1717 66 1593
-0.006 _____________________________
__________________________________________________
plt 0.05
CONCLUSIONS

• When compared to inherited and hormonal
  influences, lifestyle factors may have relatively
  modest effects on bone density and bone mass
  accrual in essentially healthy adolescent women.
• Studies of these factors to date have had
  inconsistent methods and findings.
• Future prospective studies or randomized trials
  of sufficient size are needed to determine
  whether these factors in adolescents can be
  modified to improve bone health.

This research supported by The National
Institutes of Health (NICHD, R01HD31165)