Osteoporosis is the more serious of the two, putting the patient at severe risk of fractures in the long bones of the legs and arms, as well as hips, pelvis and back. Osteopenia is the precursor of osteoporosis, where bone density is dropping but not yet at a dangerous level.
There are no symptoms of either condition, though fractures or loss of height can be warning signs. The only way to diagnose them is through a bone densitometry test (DEXA), which uses a specialised X-ray machine to assess bones in the spine, legs and hips. These tests produce a result called a T‑score. The normal range is 0 to -1, while T-scores of -1 to -2.4 indicate osteopenia, and -2.5 and below indicate osteoporosis. A person with a T-score in the osteopenia range may still be diagnosed with osteoporosis if they have already had at least one fracture of a long bone.
Diet and exercise are not the only factors contributing to bone density. Smoking and alcohol consumption are risks, as they are for many diseases. Long-term use of some prescription medications can also have a detrimental effect.
Many people think of osteoporosis as a disease of women over 70, and while women are most prone to loss of bone density after menopause, both sexes can be affected as they age. But it is not only a disease of the elderly: even people in their 40s and 50s can be diagnosed with low bone density.
Peak bone mass usually occurs in our mid-to-late twenties, and from that point it deteriorates. Like all the cells in our bodies, bone cells are being constantly recycled and replaced, but as we age, the recycling overtakes the replacement, and we lose more bone than we lay down. Everyone has a different starting point due to their genetic disposition, sex, ethnicity, and exposure to the factors important to bone-building. Vitamins and minerals like calcium and vitamin D are key building blocks for bones, so people who don’t eat dairy or go out in the sun may be deficient. Bone density is related to muscle mass, meaning someone who exercises regularly or works in a job where they perform physical labour has an advantage, while someone who does not exercise or is very thin is at a disadvantage.