Osteoporosis is abnormal thinning and weakening of bones, causing it to fracture easily. It is usually associated with low bone mineral density (BMD) but bone fragility may happen independent of BMD particularly in the elderly.
The adverse outcome of osteoporosis is fracture of the hip, spine, wrist or other parts of the skeleton. According to The International Osteoporosis Foundation (IOF), osteoporosis causes more than 8.9 million fractures annually worldwide. It is estimated that 1 in 3 women and 1 in 5 men over 50 will experience osteoporotic fractures.
Human bone is a living tissues which is constantly being remodelled, i.e., old tissues being removed (bone resorption) and new tissues being replaced (bone formation). These processes are important for repairing broken bones following injuries as well as wear and tear from daily activities. The strength or density of bone is due to deposition of calcium phosphate on the bone matrix.
Bone metabolism is regulated by:
- Hormones – parathyroid hormone, calcitonin, oestrogen/androgen, growth hormone, thyroid hormones.
- Steroids – vitamin D, glucocorticosteroids
Bone density increases from birth until about age 25 when peak bone mass (PBM) is achieved. It is followed by about 5 years of remodelling balance. By age 30, bone resorption begins to exceed bone formation, resulting in continuous loss of bone mass at a rate of 0.3 – 0.5% per year. Hence the bones of older people are comparatively thinner and more porous especially if their diet is low in calcium and vitamin D.
Due to declining oestrogen level, bone loss speeds up rapidly in women after menopause.
How is osteoporosis diagnosed?
Many people only discovered they have the problem after suffering a fracture because there is little or no symptom. Some may notice a dull ache in the bones or muscles, particularly in the lower back or neck. Sharp pains may come on suddenly at a more advance stage of the disease. The pain may linger for days or even months.
As the age advances, there might be a noticeable loss of height, accompanied by a stooped posture. This could be a sign of spinal compression fractures resulting from osteoporosis.
Based on family history, gender and age, your doctor will determine the diagnosis by measuring the bone density. The most widely used and reliable diagnostic test for osteoporosis is DXA (dual-energy x-ray absorptiometry). The computerized machine scans and measures a patient’s bone mineral density (BMD) at the hip and spine or other bones.
The result of BMD is compared to the reference measurement of a healthy young adult population (T-score). Osteoporosis is diagnosed if the BMD is equal to or more than 2.5 standard deviations below the T-score. A less serious condition, osteopenia, is diagnosed when the BMD is between 1 and 2.5 standard deviations below the T-score.
Causes of osteoporosis
The following are contributing factors:
Genetic factors. People of slight build, and descendants of Caucasian or Asian origins are at higher risk. Family history is significant in low bone density and osteoporotic fractures.
Age. Loss of bone mass begins at about age 30 and continues throughout life. The quality of elderly’s bones is less healthy irrespective of bone mineral density. The majority of hip fractures (90%) occur in people aged 50 and older, in particular among women.
Gender. Women are at greater risk than men because they stop producing oestrogen after menopause. Decreasing oestrogen level causes rapid bone loss for about five years during and after menopause. Three to four percent of total bone mass can be depleted during this period. This surge of bone loss will slow down after a few years. Around age 65, bone loss is about the same in both men and women.
Early menopause due to damage or surgical removal of ovaries, and abnormal or absence of menstrual periods are causes of osteoporosis too.
Androgen deficiency in men due to primary or secondary hypogonadism accelerates bone loss to a similar rate as seen in menopausal women.
Lack of calcium. Healthy and strong bones require a rich supply of calcium in the diet especially during the growth years. This is also to ensure the body has a good reserve of calcium because 99% of it is stored in the bones. Even after maximum bone mass has been achieved (around age 25), we still need to maintain adequate calcium intake in order to slow down bone loss for the rest of life.
Vitamin D deficiency. Vitamin D plays an important role in calcium metabolism. It is synthesized naturally in the skin when exposed to sunlight. It is also available in food such as fatty fish and eggs. However, Vitamin D deficiency may occur if exposure of sunlight is limited. It is a problem for people such as the elderly who are homebound or bed-ridden and not taking a proper diet.
Lack of activity. A sedentary lifestyle will lead to both bone and muscle weakness. Studies have shown that weight-bearing activities and the force of muscle pulling on the bones stimulate bone formation and retain calcium in the bones.
Cigarette smoking. The relationship between bone loss and smoking has been confirmed by numerous studies.
Excessive alcohol. The diuretic effect of alcohol may cause excess loss of calcium and other minerals through the urine. Alcohol can also decrease the absorption of calcium from the intestines and cause deficiencies in vitamin D and magnesium – both of which are important to bone health.
High sodium intake has harmful effects on the bones because it increases excess loss of calcium in the urine.
Rheumatoid arthritis and certain endocrine diseases such as hyperparathyroidism could have serious consequence on bone health.
Medications. Long term therapy of certain medications, such as glucocorticoids, anticonvulsants, and thyroid hormone, may contribute to bone demineralization.
Prevention of osteoporosis
We can’t change fixed risk factors such as genetic factors or age, but osteoporosis may be prevented or reduced to a lesser degree by modifying those risk factors involving lifestyle and habits. The ultimate aim is to stop fractures from happening.
Preventative measures should begin from young age.
- Good nutrition is essential for healthy bones, muscles and joints. A diet with the right nutrients -calcium, vitamin D, proteins, fruits and vegetables – is the best way to prevent and manage osteoporosis.
- Protein. Adequate dietary proteins are essential for achieving optimal bone mass during childhood and adolescence and for preserving bone health in later life. They are also essential components of muscles and other tissues. Meat, poultry, fish, eggs and dairy foods are good sources of animal proteins. Vegetable sources of proteins include legumes, soya products, grains, nuts and seeds. Too much red meat is unhealthy though, a small portion once or twice a week is adequate.
- Fruits and vegetables contain different types of vitamins and minerals, some or all of which have beneficial effect on bone formation and maintenance. Eat a good amount of vegetables and fruits daily to counteract the acidity produced by animal proteins.
- Calcium is an essential component of bones, and it is important for the heart, muscles and nerves to function properly. A daily intake of 1000 – 1200 mg is recommended. Cheese, milk, fatty fish, beans and seeds are rich in calcium. If diet is insufficient, take calcium supplements (common ones are calcium carbonate and calcium citrate) in divided smaller doses so that the body can absorb it better.
- Vitamin D helps the body to absorb calcium and a daily intake of 800-1,000 IU D is needed. Although vitamin D is made naturally by the skin and is available in food such as fatty fish and eggs, it may be necessary to include supplements for individuals age 50 and older, especially those who live a sedentary life. Vitamin D is available over the counter as vitamin D2 and vitamin D3 (cholecalciferol).
- Hormone replacement therapy. Since postmenopausal women are most likely to suffer osteoporosis and fractures, it is prudent to seek counsel about hormone replacement therapy, or alternatives, before menopause commences.
- Regular weight-bearing and muscle-strengthening exercise such as walking, jogging, dancing and weight training are beneficial at any age. These activities stimulate bone formation and maintain bone density, thus reduce the likelihood of osteoporosis. However, if you already have osteoporosis or osteopenia, talk to your doctor first or get help from a physiotherapist before beginning any exercise programme.
- Stop smoking and avoid excessive alcohol.
In conclusion, the best strategy for prevention of osteoporosis is a lifetime habit of weight-bearing exercise, avoid smoking and alcohol, and getting good nutrition from plenty of fruits and vegetables, low-fat dairy, fish and poultry, nuts, and legumes.