Osteoporosis can be divided into two types: primary and secondary osteoporosis. Primary osteoporosis is the more common of the two. Secondary osteoporosis is usually the result of an identifiable agent or disease process that causes the bone loss.
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Although the exact cause of primary osteoporosis is not always clear, a number of risk factors are known to increase the chances of developing this disease.
Remember - an individual may have these risk factors and not develop osteoporosis. Conversely, many people may have no apparent risk factors and develop osteoporotic fractures.
Risk factors for osteoporotic fractures
(A) Decreased bone strength
(i) Genetic Factors
Elderly females
Family history of osteoporosis
White, Asian and Mixed-race origin
Excessive leanness
(ii) Lifestyle factors
Alcohol abuse
Heavy smoking
Malnutrition
Sedentary lifestyle
Chronic immobilisation
Excessive exercise plus low energy intake
(iii) Diseases/drugs
Hormonal disorders (Cushing's; hypogonadism; hyperthyroidism; type I diabetes).
Malignant diseases (e.g myeloma; solid tumours)
Gut disorders (e.g. Gastrectomy; inflammatory bowel disease; malabsorption syndromes)
Negative calcium balance resulting in overproduction of parathyroid hormone
(B) Increased propensity to fall
Mental impairment*
Institutionalisation
Gait and balance disorders*
Weakness and immobility
Visual impairment
Environmental hazards/accidents
History of falls
* Increased by alcohol and drugs like sedatives, anti-depressants, antihypertensive drugs and anti-diabetes agents.
Gender, Age and Race
The peak bone mass of women, which is reached at 25-30 years, is usually about 10-25% less than that of men. After peak bone mass is reached, bone mass gradually declines in both women and men. Because of the rapid bone loss during the menopause, osteoporosis occurs more frequently in women than in men, who have no well-defined “andropause”- men lose sex hormones (testosterone) at a much slower rate.
Although osteoporosis is not a normal part of ageing, the likelihood of developing this disease and associated fractures becomes greater the longer you live.
South African White, Asian and Coloured populations are at higher risk to develop osteoporosis than Blacks. Current research is under way to determine why.
Heredity
Genetic factors play an important role in achieving adult peak bone mass. This is apparent in females where those with mothers suffering from spinal osteoporosis, tend to have lower bone densities.
Peak bone mass can however be influenced by calcium intake, exercise, hormonal factors and general health.
Body Build
Short, small framed individuals with low body weight have less bone to lose than larger, big boned women. Fat tissue is an important source of oestrogen production- petite women often have lower blood levels of this bone protective hormone.
Reproductive History
The female sex hormone, oestrogen, protects against bone loss. A premature menopause (before age 45), whether spontaneous, or surgically induced, markedly increases the risk of osteoporosis.
Not breastfeeding also appears to incur additional risk, whereas pregnancy with its accompanying high levels of oestrogen, actually protects against bone loss. A rare form of pregnancy-induced osteoporosis is however, well documented.
A decrease in testosterone levels of men can also result in bone loss and osteoporotic fractures. Up to 30% of men with osteoporosis have low testosterone levels.
Diet
A variety of nutritional factors influence bone health and a balanced diet containing adequate calories, minerals, vitamins and other nutrients is required to build and maintain strong bones. Sufficient calories, protein and Vitamin C are required for normal collagen synthesis.
Excessive phosphorous, protein and salt intake may enhance the excretion of calcium in the urine.
Caffeine has still to be proven harmful to bone.
Calcium is probably the most important nutrient needed for a healthy skeleton- especially in children, pregnant or lactating women and the elderly.
Calcium is important for bone, muscle, heart, nerve and blood cells to function normally. We lose calcium in urine and stools every day. It is therefore important to balance this loss with an adequate intake of calcium. If there is more calcium loss than intake, calcium gets released from bones and a longstanding depletion can lead to a decrease in bone mass.
Lack of exercise
Mechanical muscle-pull on bone is the only physiological way to stimulate bone formation. Immobilisation causes a dramatic decrease in bone tissue and 20-40% of bone mass can be lost within a 2 year period. Weight-bearing exercises like walking, jogging, dancing etc. are important to prevent bone loss.
Over-training in both men and women can also lead to bone loss.
Alcohol
Studies have shown that the intake of one alcoholic drink per day in women and two per day in men should not be exceeded as this can lead to osteoporosis.
Chronic alcoholism is associated with significant bone-loss in nearly 50% of cases and alcohol has a direct toxic effect on bone.
Smoking
Women who smoke tend to have lower blood levels of oestrogen, a lower body mass and tend to go through an earlier menopause than non-smokers. Bone mass in smokers is generally 15-25% lower than non-smokers.
Medications
The long-term (more than six months) use of glucocorticoids (e.g. cortisone used for treating asthma, eczema, arthritis, etc.) is an important cause of osteoporosis.
Other drugs known to influence bone formation negatively include anti-epileptic agents, certain diuretics, anti-coagulants, immuno-suppressive drugs and aluminium-containing antacids. Patients on thyroid hormone replacement therapy should have there hormone levels checked regularly, since excess thyroid hormone can also result in bone loss.
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