Understanding Osteoporosis
By Suburban Diagnostics
Osteoporosis is characterised by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. It may be either primary (idiopathic) or occurring secondary due to a number of causes. Osteopenia is a premonitory condition that occurs prior to osteoporosis; in osteopenia bone mass (or bone density) decreases but does not reach the point where there is an increased risk of fracture.
Osteopenia and osteoporosis are diagnosed by bone mineral density (BMD) tests. Experts agree that the most useful and reliable bone density test is dual-energy x-ray absorptiometry or DXA. DXA provides precise measurements of bone density at important bone sites with minimal radiation. The results of a DXA scan are interpreted relative to 2 norms – healthy young adults (T-score) and age-matched adults (z-score).
According to the WHO, osteoporosis is defined based on the following t-scores:
A T-score within 1 standard deviation (+1 or -1) of the young adult mean indicates normal bone density.
A T-score of 1 to 2.5 standard deviations below the young adult mean (-1 to -2.5 SD) indicates low bone mass - osteopenia.
A T-score of 2.5 standard deviations or more below the young adult means (more than -2.5 SD) indicates the presence of osteoporosis.
The risk for bone fractures doubles with every standard deviation below normal – hence a person with a T-score of -2 has twice the risk of fracture as someone with a T-score of -1.
At Suburban Diagnostics, we conducted an analysis on the bone densities (as indicated by t-scores) of more than 4500 adults over the age of 30 in the past 6 years.
It was seen that a higher proportion of males had lower bone density than normal (t-scores in the range for osteopenia) in the 30-39 and 40-49 age groups compared to females in the same age groups – 41.1% and 50.0% respectively in males versus 31.1% and 40.0% in females.
4.3% of males in the 30-39 age group had t-score in the osteoporotic range as compared to 2% in females for the same age group. In the 40-49 age group it was 6.5% for males and 4.2% for females.
In the 50-59 age group and the 60+ age groups, women had a much higher osteoporotic rate when compared to men. Approximately nineteen % of women in the 50-59 age group and 36.9% in the 60+ age groups had t-scores consistent with osteoporosis. In men, it was 16.5% and 18.2% in the 50-59 age group and 60+ age group respectively.
What this seems to indicate is that contrary to the popular belief males are just as prone for osteoporosis as females.
What are the causes of osteoporosis?
Genetic factors account for as much as 80% of the variance in peak bone mass, with environmental factors, exercise, diet and age at puberty accounting for the remaining 20%. Bone loss starts usually between the ages of 35 and 45 in both sexes and continues till the end of life. In the case of women, this bone loss is accelerated by the onset of menopause. Smoking, consumption of alcohol, lack of exercise, vitamin D deficiency can all increase the rate of bone loss.
Osteoporosis can also be caused as an effect of other conditions such as reduced sex hormones (hypogonadism), reduced thyroid hormones (hyperthyroidism), solid tumours, bone marrow cancers such as multiple myeloma etc. It may also result from intakes of drugs like corticosteroids and anticonvulsants. Alcohol abuse can lead to secondary osteoporosis. In fact, up to 30% of women and 55% of men with symptomatic vertebral crush fractures have an underlying cause of secondary osteoporosis.
How does one prevent osteoporosis?
There are a number of lifestyle changes to reduce bone loss. Of all the preventive measures, the one with the greatest amount of evidence supporting its efficacy is regular exercise. According to the NHS (UK), regular exercise is essential and adults between the ages of 19 and 64 should indulge in at least 150 minutes of moderate-intensity aerobic exercise. The NHS (UK) also mentions that weight-bearing exercise and resistance exercise as being particularly important in improving bone density and preventing osteoporosis.
Other measures include a healthy balanced diet rich in calcium, vitamin D and protein, quitting smoking and limiting alcohol intake.
You can also check your risk of the fracture using an online Fracture Risk Assessment Tool (FRAX). This was developed to determine fracture risk even in the absence of a BMD test. However, the tool gives a more accurate result if you include your BMD scan results.