Epidemiology to the rescue?

The current issue of the Journal of Bone and Mineral Research (Volume 24, #5) has three new epidemiologic studies related to bone health and fracture risk.

The first presents data from the NHANES III population study conducted by the CDC and evaluates the effect of dietary calcium intake on bone mineral density as a function of 25 hydroxyvitamin D levels (25OHD). In men, there was no apparent association between a calcium intake >566 g/day, BMD or 25OHD. Only in women with the lowest values for 25OHD did a higher calcium intake have a beneficial effect on BMD. In men and women, 25OHD levels were the dominant predictor of BMD in relation to calcium intake.

The take home message: the skeleton depends on vitamin D and calcium for optimum health throughout life. Both are readily available over the counter; both are inexpensive in relation to other "preventive” therapies; both are free of adverse effects for almost all persons if taken in the recommended amounts (1,000-1,500 mg/day for calcium from diet and/or supplement and 1,000 units/day for vitamin D). Unless there is a reason to suspect a malabsorption syndrome, vitamin D supplements should be recommended without need to perform any measurement of 25OHD.

The second study presents data from the Study of Osteoporotic Fractures (SOF), an National Institutes of Health-funded prospective study of determinants of BMD and fractures in older women from which much important data has been learned. The study looked at risk factors for the severity and type of hip fractures focusing on whether a femoral neck or intertrochanteric fracture was non-displaced or displaced. The question is important because mortality from femoral neck fractures is greater in those with a displaced fractured compared with a non-displaced femoral neck fracture. The best functional status six months post-fracture was best for those with undisplaced femoral neck fractures and worst for those with unstable intertrochanteric fractures. To me, that seems intuitively to make sense and underscores the importance for conducting this analysis. But the authors go on to report that, “Of interest, only pre-injury function was an independent predictor of functional outcome or mortality, rather than fracture type.” An important finding in the study was that the lower the BMD, the lower the likelihood of a displaced fracture, consistent with the hypothesis that it takes less trauma to fracture a weak bone than a stronger one.

The take home message: optimizing bone health is essential but it may go for naught if we don’t take the time to instruct the patient about safety and fall prevention both inside and outside the home! I have found that to be a hard message to get across to many of my patients, but it is an essential message.

The third study was also a prospective study with hip fracture as the outcome and it introduced me to something I had not previously considered. It was conducted as part of the Europeans Prospective Investigation into Cancer-Norfolk Study and looked at a very simple in-office tool — FEV1. A 1 L decrease in FEV1 was associated with less bone health assessed using heel ultrasound — not a well-established diagnostic tool for pre-fracture osteoporosis but a good predictor of hip fracture risk. The greater the FEV1, the lower the risk of hip fracture in men and women, independent of age, smoking, BMI, steroid use or history of fracture.

The take home message: I’m not sure yet since this is new to me, but since it was statistically significant — independent of five known risk factors for osteoporosis and fracture — it is certainly something to keep in mind. If FEV1 is already part of your practice, consider getting the measurement in patients you are assessing/following for osteoporosis.