FACTORS EFFECTS ON OSTEOPOROSIS

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.