ORIGINAL ARTICLE J. A. Pereira Silva Æ F. Costa Dias Æ J. E. Fonseca H. Canhao Æ C. Resende Æ M. Viana Queiroz Low bone mineral density in professional scuba divers Received: 28 November 2002 / Accepted: 15 July 2003 / Published online: 13 January 2004 Ó Clinical Rheumatology 2004 Abstract Scuba diving is associated with a 90% reduction in effective weight and with the loss of a weight-bearing effect on joints. These conditions are very similar to the continuous weightlessness that occurs in spaceflight and bed-rest, which are clearly associated with significant bone mass loss. Here, we studied the bone mineral den- sity (BMD) of 66 professional scuba divers using a dual- photon densitometer, and have depicted a reduction in the BMD in comparison to a matched control group of non-divers. Our results suggest that diving is also an activity where the unloading effect alters bone metabo- lism, leading to a reduction in BMD. Keywords Bone mineral density Æ Osteoporosis Æ Risk factors Æ Scuba diving Æ Spaceflight Abbreviations BMD Bone mineral density Introduction Scuba diving is associated with a 90% reduction in effective weight and with the loss of a weight-bearing effect on joints, owing to loss of contact with the ground. These conditions are very similar to the continuous weightlessness that occurs in spaceflight and bed-rest, which are clearly associated with significant bone mass loss. In fact, when the skeleton is unloaded, because of spinal-cord injury, neuromyopathy, bed-rest or micro- gravity, about 1–2% of the bone mineral density is lost at selected skeletal sites each month [1]. Unloading of the skeleton has been shown to cause an increase in the relationship between bone resorption and bone forma- tion, leading to an increase in serum calcium concen- tration and, subsequently, to a decrease in the synthesis and secretion of parathyroid hormone. In addition, the induced low levels of parathyroid hormone will cause an increased calcium excretion and decreased production of 1,25-dihydroxivitamin D, further aggravating the nega- tive calcium balance. Therefore, this mechanism creates a situation in which the body depends on bone calcium to maintain serum calcium levels.[2, 3, 4] The effect of prolonged scuba diving on bone is currently unknown. We studied a population of pro- fessional scuba divers and documented a significant de- crease in femoral neck bone mineral density compared with the control group. Material and methods Sixty-six randomly selected professional scuba divers working in the Portuguese navy, all male, with a mean age of 33.5±6.5 years and a mean diving time of 31793±19591 min during the last 5 years, were submitted to a bone mineral density (BMD) measure- ment with a dual-photon densitometer (DXA, Hologic) and asked about osteoporotic risk factors. A control group of 47 men working in the Portuguese navy, randomly selected, all male, with a mean age of 34.8±8.5, were also submitted to the same protocol. The same investigator (FCD) performed all the DXA analyses and all the interviews for assessment of osteoporotic risk factors. The protocol for the assessment of osteoporotic risk factors included evaluation of body mass; tobacco consumption (number of ciga- rettes per day); coffee (number of cups per day) and ethanol con- sumption (grams per day); calcium ingestion (mg per day); duration (minutes per week) of weight-bearing sporting activity; and diving time (total minutes during the last 5 years). Statistical analysis was performed using the Student’s t-test for the comparison of osteoporotic risk factors, and DXA results between the two groups and simple regression analysis were used to evaluate the effect of diving time on DXA results. Results As can be observed in Table 1, no significant differ- ences were observed in osteoporotic risk factors be- tween the divers and the control group. However, Clin Rheumatol (2004) 23: 19–20 DOI 10.1007/s10067-003-0787-1 J. A. Pereira Silva Æ F. Costa Dias Æ J. E. Fonseca (&) H. Canhao Æ C. Resende Æ M. Viana Queiroz Rheumatology Unit, Santa Maria Hospital, Av. Prof Egas Moniz, 1600, Lisbon, Portugal E-mail: jefonseca@netcabo.pt Tel.: +351-96-9049532