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Wednesday February 23, 2011
Osteoporosis on the rise
By Dr C.S. FOO
Not trivial: The slightest external force can easily break brittle bones. Osteoporosis has developed into epidemic proportions, affecting more women than men, and has its roots in childhood and early adult life.
HERE are a few humorous anecdotes of people breaking their bones in the confines of their homes. One old dear set the alarm, but as she stretched to turn off the ringing, she heard and felt a painful “clock” – her collar bone caved in! An old friend’s mother had a mild cough and a sneeze, and she broke six fragile ribs in unison. A makcik was turning over the Hari Raya rendang a little too enthusiastically, and instead of breaking the ladle, fractured her arm. Yet another sat on her rear too hard and fast and ended with a painful height reduction, compliments of a crushed spine.
“Osteon” and “poro” are two Greek words that mean porous bones, a.k.a. osteoporosis. Without bones, we would be just a gigantic lump of protoplasm (yes, we know a few of those). Apart from maintaining the physical framework of the body and protecting some vital assets, bone is living dynamic tissue with a multitude of physiological functions – a factory for our blood cells and a storehouse of various minerals. Bone is like a home under constant renovation, and it is faster to break down the wall than to construct one. The continuous process of new bone addition (formation) and deletion (resorption) is called bone remodeling, and at least 10% is undergoing turnover at any one time. New bone deposition is attributed to specialised cells known as osteoblasts (the builder), while osteoclasts (the destroyer) are the bane of bone loss. Anyone who has chewed on a drumstick to the bone might have appreciated some anatomical peculiarities of what is left on the plate. To snap the bone in two needs a little strength, and what confers the bone’s resilience to breakage is the outer layer of hard bone (cortical bone), which is made up of a hardened matrix of collagen and various mineral deposits of calcium, magnesium, boron and phosphorous, among others. In the centre is the less delectable marrow, also known as the spongy bone, comprising mainly connective tissue and cellular components interwoven into a honeycomb-like structure.In an old hen with osteoporosis (still referring to where the drumstick came from, of course), the cortical (hard) bone is thinner and the honeycombing of the spongy bone is sparser. The last time I sunk my dentures into a bar of crunchies, I could not help but notice similarities between a chocolate and the spinal vertebrae – coated on the outside and crunchy on the inside. A slightly excessive force can cause structural compression in an osteoporotic spine.
The numbers game
Osteoporosis has developed into epidemic proportions, affecting more women than men, and has its roots in childhood (some authors categorise osteoporosis as a paediatric disease) and early adult life. Males generally have a fatter bank account as far as bone mass is concerned. Bone growth reaches the maximum in strength and hardness by age 30. This is known as peak bone mass. Boys reach 90% of peak bone mass by age 20, whilst girls achieve it earlier around age 18, rendering the male species extended growth potential, answering in part the question why guys are taller. The best time to invest in the bone account is during youth. Exercise, good nutrition, and adequate calcium intake pay long term dividends. Just like a financial account, the bone account is subject to deposits and withdrawals. In youth, deposits exceed withdrawal, until a period of steady exchange in the 30s. Unfortunately, the gentler gender succumbs to far more withdrawal than deposits after age 40, leading to a net loss of bone mass. Multiple pregnancies herald premature onset of bone deficit. As the ovaries start to wrinkle and the eternal spring of oestrogen trickles, culminating to a dry spell, that phase of mood swings, hot flushes, dryness, and loss of libido collectively known as menopause stamps its sovereignty. Loss of oestrogen accelerates the diminishing bone mass, leading to a greater tendency to pathological fracture. Simply put, brittle bones that break with trivial force. To dent the glee in the ageing male, there is no escape from the gloom of age-related osteoporosis after the age of 75, with a ratio of one male to two females afflicted. The countries with the highest consumption of calcium-fortified dairy ironically boast of the highest incidence of osteoporosis (Norway, Sweden, Denmark, United States). The Asia Pacific region is rapidly catching up, hitting the target of a 300% increase in the last 30 years. Half of post-menopausal Malaysian women have osteoporosis, and one in three will experience an osteoporotic fracture. For age-related osteoporotic fractures, it is one in five for guys. The gold standard test (DXA – Dual energy X-ray Absorptiometry) for osteoporosis is done at specialised radiology centres that measure bone density (BMD), comparing the “hardness” and strength with that of an average young adult at peak bone mass.The assessment is based on a scoring system (T-score of more than -1 is normal, -1 to -2.5 is low bone mass [osteopaenia] and -2.5 confirms established osteoporosis) usually carried on the spine or hip, predicting a higher risk of fracture.
Bone thieves
One of the most important stimulants of bone growth is weight bearing exercise. Astronauts who walk in weightlessness in space for extended durations tread carefully upon returning to earth for fear of buckling under gravity. Dr Nicole Buckley, director for Canadian Space Agency, estimates that those guys who float around and wave to Earth’s terrestrials lose up to 2% of bone mass per month. Down at sea level, bedridden subjects lose up to 15% of bone mass within three months as immobilisation augurs bone loss. Women marathon runners have a higher risk of brittle bones as they often experience irregular menses and early menopause. Intensive training without proper nutritional counseling hastens onset of osteoporosis.
On the other hand, women who do not run around much are at risk too. Declining levels of oestrogen lead to rapid net bone loss. The “phallusy” of male andropause is subject to debate, but certainly the ageing centenarian is more than a little low on ammunition as far the male hormone, testosterone, is concerned, thereby accelerating bone deficit. Smoking, alcohol and caffeine are recreational robbers. A sooted chimney clogs up the machinery of the osteoblasts, decreasing deposition of bone. Alcohol in moderation is fine but heavy drinkers must beware of shattering more than the bottle.Taking more than two cups of coffee daily has a lifetime risk of developing osteoporosis. This may be offset by drinking at least a glass of milk a day, making my favourite cafe latte a reasonable trade off. Caffeine increases urine output (diuresis), which drags minerals along, depleting blood calcium levels. To ensure stability (homeostasis) in calcium levels, the mineral is mobilised from the bones. Poor childhood nutrition with low protein intake certainly leads to reduced peak bone mass, but conversely, an excessively high protein diet induces blood acidity and more urinary excretion of calcium, thereby leaching bone calcium stores. Carbonated beverages contain higher concentrations of phosphates, which translate to lower blood calcium levels, again dragging out this mineral from the bones.
The infamy of sugar and salt has found its way to a wide array of diseases, and certainly, brittle bones is no exception.Pharmacological robbers include drugs and certain supplements. Steroid is a notorious pill that heals and kills. It is lifesaving in many circumstances, but there are long term deleterious effects on bone density. Pre-formed and synthetic vitamin A promote porosity of bones.Non-modifiable factors that enhance bone loss include hormonal disturbances, genetic links and gender selection upon conception (tough luck for double X chromosomes).
Consolidation of assets
Once the bone stealers have been identified, the logic of avoidance and management is seemingly simple.
In reality, it is not readily executed, for it is simpler not to do anything. The neglect of the bone bank continues through adulthood and beyond. Sound nutrition, exercise and calcium supplements at an early age go a long way to prevent early onset of osteoporosis. A diet high in fruits and vegetables reduces the acidity of meat and dairy consumption. On top of this, they are a great source of many various vitamins and minerals.
To ensure ongoing build-up of bones, a constant supply of raw materials must be guaranteed. The daily calcium intake recommended for females at various ages range from 1,000mg for a young adult to 1,500mg in a peri-menopausal woman). The absorption rate of calcium differs according to various sources – zero for limestone (the most natural form of calcium), 30% to 40% from whole foods, 30% from inorganic salts (e.g. calcium carbonate) and 50% to 70% from the chelated form (e.g. calcium citrate). However, a good dose of sunshine without additional vitamin D is insufficient for optimal absorption of calcium. Dairy products and tofu are rich sources of calcium. Taking four to five glasses of milk a day potentially meets the daily requirements for calcium. Ironically the highest incidence of osteoporosis follows the population that drink the most milk. In a trial conducted by Harvard’s Nurses Study, the relative incidence of hip factures of women who drank more than two glasses of milk a day is 45% greater than those who drank one. Osteoporosis has been called a paediatric (childhood) disease with geriatric consequences. Accumulation of bone wealth must commence from childhood, thus laying the foundation for strong skeletal elements, in preparation for the dwindling assets of ageing.
Dr C.S. Foo is a medical practitioner. For more information, e-mail starhealth@thestar.com.my.
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There are a lot of information regarding osteoporosis from this article. Osteoporosis attacks people at alarming rate now, especially post-menopausal women. I hope this article alerts us, as becoming future doctors , about this disease in relation to human musculoskeletal system.
p/s = for all the 2nd year students, enjoy memorising the names of muscles ek...huhuhu
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