In the past two decades, obstructive sleep apnea syndrome (OSAS) has been identified as a common clinical condition with high prevalence in middle-aged adults [1]. OSAS may trigger a cascade of intermediate mechanisms that are potentially harmful to the cardiovascular and metabolic system, and include sympathetic activation activity, oxidative stress, and systemic inflammation [2]. All these intermediate mechanisms may help to explain the contribution of OSAS to several diseases, including hypertension, stroke, diabetes, and cardiac arrhythmias and the increased mortality associated with the disease [3][4][5][6]. Cardiovascular morbidity and mortality associated with sleep apnea have been extensively studied in the last decade [4,7,8]. Furthermore, several former and recent studies have indicated strong association between cardiovascular diseases and osteoporosis [9-13], with the above intermediate mechanisms of OSAS to have a critical role in the common pathophysiological pathway of both diseases. Therefore, this association leads us to hypothesize that OSAS may also be responsible for the development of osteoporosis.In this issue of Sleep and Breathing, Hulya Uzkeser, and colleagues of the Ataturk University, Turkey, in their paper "Bone mineral density in patients with obstructive sleep apnea syndrome" tried to investigate the relationship between OSAS and osteoporosis by examining both the bone metabolic abnormalities and bone mineral density (BMD) in OSAS patients compared to individuals without OSAS. The authors found a significant difference between OSAS patients and the control group in relation to lumbar L1-L4 BMD, femoral neck BMD, and lumbar L1-L4 t score values, evaluating the underlying assumption of the relationship between OSAS and osteoporosis. Taking into account that there have been no previous reports about the correlation between OSAS and osteoporosis, assessed by bone mineral density, we appreciate this type of work. Furthermore, the study certainly has clinical importance as the issue of osteoporosis is very important, underestimated, and with rising prevalence. Many well-designed epidemiologic studies worldwide have demonstrated that this disease and its consequences represent a high burden on health systems due to the high costs and the resources needed for the care of patients suffering from it [14].What can these results be attributed to? There are at least three mechanisms that may potentially affect abnormal bone metabolism in OSAS: hypoxia, increased oxidative stress, and inflammation [15]. As the authors hypothesize, the balance between osteoclasts and osteoblasts is disrupted in favor of osteoclasts in the presence of hypoxia. However, the fact that they did not find any significant differences in serum Ca, P, ALP, and urinary Dpd levels in OSAS patients compared to controls is still not clear.In the literature, the first clinical indication of the adverse effects of OSAS on bone metabolism was by Tomiyama et al. [15]. The authors investigated the association between the severity o...