Factors effects on osteoporosis
Among
nutritional factors that cause bone loss, deficiencies in calcium,
vitamin D, and more recently, protein have been shown to be
associated with deficient skeletal growth or accelerated bone loss.
Vitamin K deficiency may also be associated with risk of hip
fracture. Dietary intake of phosphates may be increasing in some
populations as a result of their use as food additives and the
increase in intake of carbonated drinks. These drinks may have a
deleterious effect on bone, because they have replaced milk in the
diet of some young people, and because high intakes of phosphates
stimulate the secretion of PTH, but there is no evidence so far that
high phosphate intakes accelerate bone loss in humans.
Calcium
intake, vitamin D and osteoporosis
In
the elderly, several factors contribute to negative calcium balance.
With ageing, calcium intake decreases because of reduced consumption
of dairy products, and the absorptive capacity of the intestinal
epithelium to adapt to low calcium intake is impaired. Exposure to
sunlight and the capacity of the skin to produce vitamin D are also
reduced. The capacity of the renal tubule to reabsorb calcium, and
its responsiveness to PTH are impaired. Finally, the decease in
glomerular filtration rate observed in the elderly may contribute to
chronic hyperparathyroidism, favouring a negative bone mineral
balance and thus osteoporosis. Increasing calcium intake is certainly
an important strategy which is relatively easier to implement than
other possible preventive measures.
Protein
intake and osteoporosis
The
mechanism whereby a low protein intake has adverse effects on bone
may be due to inadequate production of IGF- 1, which exerts anabolic
effects on bone mass, not only during growth, but also during
adulthood. Protein replenishment in patients with hip fracture can
improve not only BMD, but also muscle mass and strength. These two
variables are important determinants of the likelihood and
consequences of falling and thus incidence of osteoporotic fractures.
This
observation underlines the importance of weight-bearing in the
maintenance of bone mass. At the tissue level, immobilization results
in bone resorption being greater than bone formation. At the cellular
level, immobilization increases bone reabsorption by osteoclasts
associated with a decrease in osteoblastic formation. The molecular
signal(s) perceiving the reduction in mechanical strain associated
with immobility has not been identified.
Risk
factors for osteoporotic fracture
Although
many risk factors for osteoporotic fracture have been identified,
risk factors for different fractures may differ. For example, an
early menopause is a strong risk factor for vertebral fractures, but
not for hip fracture in later life. Risk factors may be causally
related or indirect. While the former are amenable to personal
modification, environmental or therapeutic manipulation, even
indirect factors may be useful in identifying individuals at high
risk.
Trauma
Fractures
occur when skeletal loads, whether from trauma or the activities of
daily living in the case of some spine fractures, exceed the breaking
strength of bone. Falls are the most common cause of traumatic
osteoporotic fractures. The annual risk of falling increases from
about 20% in women aged 35–49 years to nearly 50% in women aged 85
years and over, and is 33% in elderly men . Although environmental
hazards play a role in many falls, up to half the falls among the
elderly are associated with organic dysfunction, including diminished
perceptions of the lower extremities and postural control, gait
abnormalities, muscular weakness, decreased reflexes or poor vision.
In addition, chronic illnesses such as neurological disorders, heart
disease, stroke, urinary incontinence, depression and impaired
cognitive function increase the risk of falling. The proportion of
falls associated with these problems increases with age , and the
risk of falling is correlated with the number of comorbid conditions
present.
Low
bone density
Risk
factors for low bone density include inadequate peak bone mass and
excessive bone loss . In addition to the accelerated bone loss seen
at the menopause, bone loss may also result from age-related
conditions such as reduced calcium absorption from the gut and
secondary hyperparathyroidism . In addition, certain medical and
surgical conditions can produce so-called “secondary”
osteoporosis. In the most comprehensive study to date, the Study of
Osteoporotic Fractures , the determinants of BMD at various skeletal
sites were assessed in a large number of Caucasian or Asian-American
women aged 65 years or over, and included greater age at menopause,
estrogen or thiazide use, non-insulin-dependent diabetes (NIDDM), and
greater height, weight, strength and dietary calcium intake, all of
which were positively associated with greater BMD at the distal
radius. In contrast, older age, cigarette smoking, caffeine intake,
prior gastric surgery and maternal history of fracture were
negatively associated with BMD at that site (53).
For the spine, greater weight, older age at menopause, a history of
osteoarthritis, greater physical activity, moderate consumption of
alcoholic beverages, treatment with diuretics and current HRT were
associated with greater BMD, while later age at menarche and a
maternal history of
fracture
were associated with lower BMD . Increasing age positively correlated
with spinal BMD in these elderly women, probably because of
hypertrophic changes in the spine. Greater BMD of the femoral neck
was positively associated with most of the same factors as those
listed for the spine, together with quadriceps strength, calcium
intake,
and a history of NIDDM . A history of maternal fracture and of prior
wrist fracture was associated with low femoral neck BMD. Greater age
was a risk factor for low BMD of the femoral neck, as it was for low
BMD of the radius. Risk factors are reviewed in greater detail below.
Previous
fracture
The
occurrence of one osteoporotic fracture may increase the risk of
future fractures. Thus in both men and women who have suffered a
distal fracture of the forearm, the risk of subsequent fractures of
the proximal femur and other skeletal sites is approximately doubled
.
Genetics
Up
to 50% of the variance in peak bone mass and some aspects of bone
architecture and geometry relevant to bone strength may be determined
genetically. . A family history of fragility fracture, and
particularly of hip fracture, can be used in the risk assessment of
patients .
Nutrition
Dietary
factors influence peak bone mass, age-related bone loss and fracture
risk. Calcium and vitamin D are particularly important since
deficiencies are potentially correctable.
Calcium
The
most consistent effects of calcium supplementation are observed in
the appendicular skeleton, while effects on spinal bone appear to be
transient. Older women seem to be more responsive to such
supplementation than younger postmenopausal women. The relationship
between calcium intake and fracture rate is less clear. While inverse
correlations between dietary calcium intake and fracture (mainly of
the hip) have been found in some studies, no significant correlation
has been found in others and some have even shown a positive
correlation between calcium intake and hip fracture. However, in a
recent meta-analysis, it was reported that each additional gram of
calcium in the diet was associated with a 25% reduction in hip
fracture risk.
Vitamin
D
Severe
and prolonged deficiency of vitamin D results in rickets in children
and osteomalacia in adults, conditions characterized by defective
mineralization of bone. Osteomalacia will aggravate osteoporosis,
since both increase the risk of fracture. Vitamin D deficiency is
rare in Europe and the USA, but is still common in the Low levels of
circulating vitamin D are common in elderly populations in many
regions of the world and may contribute to fractures, particularly at
the hip . A positive association between serum
1a,25-dihydroxycholecalciferol
concentration and BMD was found in middle-aged and elderly women.
Vitamin D supplementation prevents the reduction in BMD that occurs
during the winter months in normal subjects.
Protein
Low
protein intake is an important determinant of peak bone mass and
therefore of the risk of osteoporosis in later life .The prevalence
of malnutrition and undernutrition increase with advancing age and in
patients with hip fracture. In the elderly, an association between
low protein intake, low BMD and reduced mobility has been reported.
This does not seem to be due to ageing itself, since healthy active
elderly people and young adults are nutritionally not very different,
in contrast to the acutely and chronically ill elderly population in
whom signs of malnutrition are common . Undernutrition may increase
the propensity to falls both by impairing coordination and reducing
muscle strength. It is also an important determinant of the
consequences of falling, since a reduction in the protective layer of
soft tissue padding decreases the force required to fracture an
osteoporotic hip.
Phosphate
A
high dietary intake of phosphate in combination with a low intake of
calcium increases serum PTH concentrations and may reduce BMD.
Vitamin
K
Low
plasma levels of vitamin K1 and K2 have been reported in patients
with hip fracture. Vitamin K is essential for the production of
gamma-carboxylated glutamyl residues present in several coagulation
factors and bone proteins, particularly osteocalcin. Vitamin K
deficiency can be assessed by measuring the undercarboxylated
fraction of osteocalcin. This fraction increases with age and is
therefore negatively related to BMD in elderly women.
Undercarboxylated osteocalcin has been reported to be a predictor of
hip fracture. However, protein–energy malnutrition is usually
associated with multiple deficiencies so that the particular
contribution of vitamin K deficiency to bone loss in undernourished
patients sustaining hip fracture is unknown.
Magnesium
and other trace elements and vitamins
Magnesium
interferes with both the production and action of PTH, and thus
indirectly affects bone metabolism. However, a specific role of
magnesium in the maintenance of bone mass during adulthood has not
yet been identified. Several trace elements are required for normal
bone metabolism. Various animal and/or ecological studies in humans
suggest that aluminum, boron, copper, fluoride, manganese, silicon,
and zinc, as well as vitamins B6, B12 and C, may all play a
protective role in the normal metabolism of bone tissue. Selective
intervention studies are still required to identify their respective
roles in the maintenance of bone mass, particularly in the elderly.
Physical
inactivity
Immobility
is an important cause of bone loss, and its detrimental effect on
bone mass is far greater than the beneficial effect of additional
exercise in an already ambulatory subject. Enforced immobility in
healthy volunteers decreases bone mineral mass, as do motor deficits
due to neurological disorders such as hemiplegia or paraplegia. Bone
mineral mass also decreases during space flights despite vigorous
physical exercise. In contrast, bone density increases in response to
physical loading and mechanical stress. In many cross-sectional
studies, a beneficial effect of weight-bearing exercise on peak bone
mass has been reported. The observation that retired adult gymnasts
have higher BMD than age-matched sedentary controls suggests the
benefits of physical
activity
outlast the termination of such activity, and the results of
randomized controlled trials suggest that certain forms of exercise
may retard bone loss. These studies also show that the skeletal site
which is maximally loaded demonstrates the greatest effect. The type
of loading also influences skeletal response.
Cigarette
smoking
Definitely
is definitely responsible for giving rise to a large number of
diseases and this includes Osteoporosis as well. Smoke often kills
the amount of calcium from the body of a person and this plays a
significant role by giving rise to this disease. It is said that the
weakness of the bones in many cases depends upon the factor that how
much a person smoke in a day. Basically smoking is something that is
considered as a calcium absorber as well as the killer of the tissues
of the bones. The bone tissues are killed in a very large amount and
when the tissues of the bones are killing the person’s face weak
bone which is considered as Osteoporosis.
Alcohol
consumption
Just
like smoking alcohol also widely contributes in giving rise to this
disease and this is considered as one of the primary reasons for the
Osteoporosis in a large number of people. When a person takes alcohol
on a regular basis he/she can get affected by the Osteoporosis very
easily and in a very short period of time. Basically avoiding the
alcohol is not easy for any person and it has been said that when a
person fails in avoiding the alcohol on time probably he/she face
this problem for a long period of time in the life.
It
must be noted that because women have a weak bone density than men
and also the bone density of older people are also less. This is the
leading factor that is responsible for having the most number of
cases of Osteoporosis in women.
Body
mass index
Low
body mass index (BMI) is associated with lower peak bone mass, and an
adverse influence on bone loss . This may be the consequence of
reduced peripheral estrogen production by adipose tissue among thin
women, less mechanical loading of the skeleton, and metabolic
influences on body composition. Excessive leanness is
also
a risk factor for hip and vertebral fracture, and longitudinal
epidemiological studies have shown that accelerated weight loss is an
important determinant of the risk of hip fracture . In Europeans,
the
risk of hip fracture is increased below a threshold BMI of 19kg/m2 .
It is not known whether this threshold is also applicable to other
populations.
Sex
hormone deficiency
Primary
hypogonadism in both sexes is associated with low bone mass, and
decline in estrogen production at the menopause is the most important
factor contributing to osteoporosis in later life. In addition,
secondary amenorrhoea, as the result, e.g. of anorexia nervosa,
excessive exercise or chronic disease, results in lower peak bone
mass and increased risk of osteoporosis. Late menarche may be
associated with lower peak bone mass and higher fracture risk.
Finally, some studies indicate that the use of oral contraceptives
may be associated with higher bone mass, although this finding has
not been universal. A premature menopause, particularly
when
surgically induced before age 45 years, is a strong determinant of
bone density and increased risk of fracture.
