The silent disease

Published : Jan 16, 2004 00:00 IST

Although the incidence of osteoporosis is high in India, lack of awareness about the disease delays diagnosis and preventive treatment.

OSTEOPOROSIS, literally meaning "porous bones", is the breakdown of bones, which together constitute the hardest part of the human body. Over 300 million people suffer from osteoporosis in India without realising that every osteoporosis-related bone fracture doubles the risk of death.

What causes osteoporosis? Minerals mix with water to form a hard cement-like substance called hydroxyapatite. Calcium is its principal ingredient. Calcium also plays an important role in transmitting signals to nerves and muscles and is therefore important in regulating the heart rate, muscle contractions, blood pressure and other bodily functions. To keep these functions regulated, the calcium in the blood must be maintained at a certain level. When it drops to a very low level, the body replenishes it with calcium from the bone - a living and growing tissue composed of a network of collagen fibres inlaid with calcium and phosphate.

`Resorption', the process of releasing calcium from bones into the blood, results in the breakdown of bones. By another process called `formation', the bones get rebuilt. Together, the two processes constitute bone remodelling. The continuous remodelling cycle serves to supply the body with the calcium it needs and maintains the skeleton structure and strength by replacing old bones with new ones. When formation exceeds resorption, the bone mass increases. When resorption takes place faster than formation, there is a loss of bone mass. Continued excessive bone loss leads to osteoporosis.

During the early years of life, formation is greater than resorption and the bone mass increases. Maximum or peak bone mass is reached around the age of 30 in a healthy adult. After that, resorption is faster than formation and the bone mass decreases. While gradual bone loss is normal to aging, it is those who fail to achieve optimal peak bone mass and/or those with accelerated bone loss who are at the greatest risk of osteoporosis.

Osteoporosis is defined in terms of standard deviations from the average peak bone mass. The World Health Organisation (WHO) defines osteoporosis as a bone mineral density (or bone mass) that is 2.5 standard deviations below peak bone mass. Those with standard deviations of 1-2.5 below the norm are said to have osteopenia or low bone mass. Individuals within one standard deviation below the norm are considered to be at low risk of osteoporotic fracture.

Bone fracture is the biggest risk for osteoporosis patients. Any bone can be affected, but the most serious ones are fractures of the hip and the spine. Over 20 per cent of people with hip fracture die owing to resulting complications, while 50 per cent of those who survive end up with a permanent disability. Spine fractures can reduce the height of people by 30-40 cm and after one spine fracture, the risk of fractures goes up dramatically.

Every year, over 1.5 million fractures are caused by osteoporosis - of this, more than 3,00,000 are fractures of the hip and 7,00,000 of the vertebrae. On an average, one in two women and one in eight men over 50 years of age will have an osteoporosis-related fracture in their lifetime. But in India, the incidence is even higher - one in three-four women and one in six-eight men get osteoporosis before the age of 50. More women die of osteoporosis fractures than of breast and ovarian cancers put together. Osteoporosis fractures occur 10-20 years earlier in Indians compared to people in Western countries. The incidence of the disease among men is also higher than in Western countries.

Unfortunately, osteoporosis shows no symptom and is often diagnosed only after a fracture, by which time the patient may have suffered considerable bone loss.

According to experts, osteoporosis is just not calcium deficiency. It is a combination of the loss of the organic matter in the bone, which gives it elasticity, and the inorganic matter, made up of substances such as calcium and phosphorous, which gives it strength. In the early stages osteoporosis is painless and hence it is often called the "silent disease". But as it progresses, it causes back pain and, after some time, curving of spine and loss of height, and then frequent fractures. Though osteoporosis can be slowed, the associated bone loss cannot be made up beyond a certain level.

Osteoporosis fractures lead to significant lifestyle changes. They can greatly reduce a person's independence, quality of life and even survival rate. Fractures of the spinal vertebrae, called compressions, cause progressive change in the shape of the spine and the back; the vertebrae may even collapse without any warning. A person may lose height or develop a pronounced curvature of the spine, known as a "dowager's hump". The fear of fracture raises the risk levels of even such simple pleasures of life as walking, dressing or shopping. This can lead to depression and other psychological problems.

The most reliable method to measure bone mass is the dual-energy X-ray absorptiometry, or DEXA, scan. A modification of DEXA, called peripheral DEXA or pDEXA, measures bone density in the wrist. A radiation-free technique that has been developed recently is quantitative ultrasound, which measures bone density of the calcaneus (heel) bone.

Since the genetic make-up is the main factor behind the disease, some people are more likely to develop osteoporosis than others. While 30 per cent of those who have osteoporosis have no identifiable cause, there are two types of risk factors - "internal" or uncontrollable, and "external" or controllable. The internal factors, or those that occur naturally, include thin or small body frame; early estrogen deficiency that occur in women who reach menopause before the age of 45 and premenopausal women with amenorrhea (absence of menstrual cycles); low testosterone levels or androgen deficiency in men; gender (women are at higher risk) and old age; ethnicity and race (Asians, native Americans, white Hispanics and white non-Hispanic women are at highest risk); and family history.

The "external" factors are those that result from certain lifestyle choices that reduce calcium and vitamin D intake. These factors include sedentary lifestyle; cigarette smoking (tobacco lowers estrogen levels in women and may have a similar effect on sex hormones in men); excessive intake of alcohol, which can interfere with the absorption of nutrients needed to preserve bones; excessively caffeinated beverages, which can lead to calcium loss; eating disorders such as anorexia nervosa and bulimia, which can lead to inadequate intake or excessive elimination of bone-building nutrients; prolonged use of certain medications such as gluco-corticoids, a group of anti-inflammatory medications used to treat conditions such as asthma, arthritis and some cancers, and excessive intake of medications such as thyroid hormone and some anti-convulsants, which can lead to bone mass loss.

PREVENTION of osteoporosis is a life-long effort that has to start from childhood. One of the most important factors in preventing osteoporosis is achieving optimal peak bone mass during childhood, adolescence and early adulthood. Much of the peak bone mass achieved is determined genetically. However, there are several controllable factors that can increase bone mass. These include a balanced diet, adequate intake of vitamin D and calcium, and exercise.

According to experts, vitamin D is said to be the `key' that unlocks the door to the body to let calcium in. Without vitamin D, the body cannot use calcium well even if it gets enough of the mineral. The exact optimal daily dose of vitamin D has not been determined, but most experts recommend 400-800 IU of vitamin D daily; less than 400 IU a day does not lead to full benefits from calcium while more than 800 IU a day can be harmful. Accumulating a life-long bank account of calcium is the answer, and what is crucial is to build on this "bank account" early.

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