Association between urine cotinine levels and bone mineral density in lumbar spine and femoral neck among adult males

STUDY DESIGN.: Cross-sectional study. OBJECTIVE.: To investigate an association between tobacco exposure as determined by urine cotinine and bone mineral density (BMD) in femoral neck and lumbar spine. SUMMARY OF BACKGROUND DATA.: Loss of BMD is 1 of the major causes of spine and femoral neck fractures in the elderly population. There is limited literature on risk factors to loss of BMD, in particular, among males. METHODS.: We analyzed data of 770 males older than 30 years, which were collected from the cross-sectional Fifth Korea National Health and Nutrition Examination Survey, with t tests, analysis of variance, and multiple linear regressions. RESULTS.: The means of femoral neck BMD (T score) significantly decreased with increasing age, -0.08, -0.63, and -1.49 in males aged 30 to 40 years, 50 to 69 years, and 70 to 95 years, respectively (P < 0.001). The same trend was observed in lumbar spine BMD. Although education (P < 0.001) and income (P = 0.021) were associated with femoral neck T score, only education (P = 0.034) was associated with lumbar spine T score. The group who had urine cotinine level of more than 10 μg/mL (active smokers or nonsmokers who were exposed to second-hand smoking) had lower femoral neck T score (-0.43 ± 0.98) than the group who had cotinine level of 10 μg/mL or less (-0.33 ± 0.89) (P = 0.114). In the multiple linear regressions, age, urine cotinine level, and body mass index were statistically related to femoral neck and lumbar spine T score. CONCLUSION.: Our findings suggest that tobacco exposure by active or passive smoking and lower body mass index seem to exert a negative effect on femoral neck and lumbar spine BMD.