Osteoporosis is the most common type of bone disorder, affecting an estimated 10 million Americans. It is a chronic condition characterized by reduced bone strength, low bone mass, and a higher risk of bone fracture, especially at the hip, spine, and wrist. If you are over the age of 50, there is a 55% chance that you are at increased risk for osteoporosis or have it already. The risk of osteoporosis increases with age; it is not, however, limited to older individuals.
Osteoporosis can be prevented or slowed down, but once damage to the bone has taken place, it can be difficult to reverse. Bone fractures are the main consequence of osteoporosis, and they are associated with lasting disability after they occur, especially hip fractures in older people.
For reasons that are still unclear, people with both Type 1 and Type 2 diabetes experience a higher incidence of bone fracture than the general population, even though people with Type 2 diabetes tend to have above-average bone density. It is especially important, then, for people with diabetes to know about osteoporosis, to have their risk of fracture evaluated by medical professionals, and to find out what they can do to make their bones as strong and healthy as possible.
Bone mineral density
One way health-care providers evaluate a person’s risk of osteoporosis is to do a bone mineral density (BMD) test. The most common test uses x-ray beams, is painless, and can be done in a matter of minutes.
BMD is a core indicator of bone strength. A test for BMD measures the amount of a mineral, usually calcium, in a bone. This measurement is then compared to the pooled measurements of a group of healthy young adults using a statistical indicator called a standard deviation. If the BMD of the person being evaluated is 2.5 standard deviations or more below the average reference-group BMD, that person is considered to have osteoporosis. If BMD is 1—2.5 standard deviations below the reference-group average, it indicates a less severe condition called osteopenia, or low bone mass. Lower BMD usually means that the bone is weaker. In general, people with Type 1 diabetes have lower BMD and people with Type 2 diabetes have higher BMD than people without diabetes with otherwise similar characteristics.
Several studies have been conducted to determine whether diabetes affects bone mineral density. However, most studies have used readings taken at only one point in time, so little is actually known about changes in BMD that occur because of diabetes. Studies that track individuals over a long period will be needed to fully understand how diabetes affects BMD. The existing studies on diabetes and bone health, however, have produced some important findings.
Fracture risk studies
Two recent comprehensive meta-analyses found that people with Type 1 diabetes had a risk of hip fracture 6.3–6.9 times as high as people without diabetes; people with Type 2 diabetes had a risk 1.4–1.7 times as high. (A meta-analysis is a statistical way to combine the results of many studies that address similar questions. It is helpful in this case to get the most accurate estimate of fracture risk.) While the increased risk accompanying Type 2 diabetes may be small, it represents a risk associated only with diabetes, not with sex, age, physical activity level, or body-mass index. The small number of studies on Type 1 diabetes and fracture made it impossible to rule out other fracture risk factors such as sex, age, physical activity, and body-mass index. Although there were not enough data on diabetic complications to thoroughly evaluate their impact, individuals with more complications were generally found to have a higher fracture risk. An important finding from several recent studies was that an increased risk of fracture was present among people with both Type 1 and Type 2 diabetes at middle age, not just among older individuals.