Longitudinal Changes in Bone Mineral Density for Healthy Female Elders in Southern Taiwan

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Longitudinal Changes in Bone Mineral Density for
Healthy Female Elders in Southern Taiwan Chen
CH, Chang JK, Ho ML, Hung SH, Chiu HC Kaohsiung
Medical University, Kaohsiung, Taiwan
2009 February
INTRODUCTION Osteoporosis is one of the most
important conditions in geriatric studies. With
the increase of age, the incidence of
osteoporosis-related fracture increases.
Longitudinal data on bone decline for Chinese
elderly are sparse, especially in the healthy
aged female. We hypothesized that the bone loss
rate at different age group is different in
female. Thus, we performed a prospectively
longitudinal cohort study on healthy participants
and aged 61 and over, at an interval of two years
to gather baseline information about the course
of senile osteoporosis in the elderly male in
southern Taiwan. The first goal of this study was
to provide the baseline data of BMD in the
healthy aged male in southern Taiwan. The second
goal of this study was to compare the difference
of BMD loss rate at different sites of the
proximal femur among different age
groups.. METHODS A prospective cohort study was
conducted. We screen 1500 subjects with age 61
and above. The screening progress includes three
phases. First, the junior nurse screened the
potential candidates using a structured
questionnaire. Those with one of the following
conditions are excluded lower leg arthropathy
leading to inability of climbing two floors at
once, and the need to take a break during a short
distance of walking for 2 blocks. Those with one
of the chronic diseases are also excluded, such
as spinal problems (spondylosis, sciatica,
kyphosis, or scoliosis), gouty arthritis, and the
history of established osteoporosis. In total, 60
females were qualified for entering second phase
study. The qualified elderly were invited to our
university hospital for the examinations on chest
x-ray, laboratory tests, and pulmonary function.
Two senior physicians responsible for examining
and reading the results made decisions on who are
qualified for the third phase of this study, i.e.
BMD examination. Among 70 qualified subjects, 63
were eligible for hip evaluation and 60 (95
participation rate) have completed the hip BMD
including femoral neck, Wards triangle and great
trochanter. Two years after the initial
examination, 53 elderly returned in 2002 for the
second screen test and 50 of them finished hip
BMD evaluation. Totally 50 female had completed
follow-up. BMD was got at the initial visit and 2
years later. The subjects were divided into 2
groups age 61-70 and age above 71. Linear
regression was performed between aging and bone
loss. Pair-t test was used for BMD changes
between the intervals. RESULTS In the initial
study, the subjects had significant bone loss
through aging by liner regression at all three
sites (Plt0.05). Two years later, there is a
significant decrease in BMD at all three sites
(Plt0.05). For the age cohort, both groups showed
a significant decrease in BMD of the 3 studying
sites (Plt0.05). There is a peak loss of BMD in
females aged 61-70 as high as 2.74 annually at
the Wards triangle. (Table 1)
The mean loss rate of BMD is about 2 to 5 times
higher in our study than Framingham study and
Rotterdam study at femoral neck. Similarly, the
mean loss rate of BMD is about 8 to 9 times
higher at the Ward triangle and 2.2 to 7.5 times
at the great trochanter than the 2 other studies.
(Table 2) The possible causes may be the
differences in gene, eating habit, and different
lifestyle. BMD is negatively related to aging in
the healthy female. The loss of BMD in the age
group of 61-70 years at the Wards triangle is
faster than other sites. The loss rate is near
the same in all three are in the group of age
above 71. Therefore, detecting the BMD at the
Wards triangle may be a reasonable method for
earlier detection of bone loss at this age group.
The bone loss in Chinese female should be
cautious because they have much more bone loss
than the Caucasians
Table 1. Bone mineral density in female 2 years
after initial examination .
Table 2 Comparison of Annual change of bone
density (g/cm2/year)
DISCUSSION From the baseline data of this study,
we found that BMD declined significantly with
aging in the proximal femur by regression in
healthy female aged 60 and more. Most of the
previous studies also proved that BMD decreasing
at most sites is related to age. Longitudinally,
BMD at all 3 studied sites decreased
significantly with increased age. We found that
the subjects in our study experienced a much
higher rate of bone loss than that of two studies
(Table 2). For example, the mean bone loss rate
at the femoral neck was 0.012 g/cm2/year in our
study as compare to 0.006 g/cm2/year in the
Framingham study and 0.0025 g/cm2/year in the
Rotterdam study.