Association between passive smoking in adulthood and phalangeal bone mineral density: results from the KRAM study-the Danish Health Examination Survey 2007-2008

The study investigates an association between phalangeal bone mineral density (BMD) and self-reported passive smoking using data on 15,038 persons (aged 18-95 years), who underwent a BMD scan in the Danish KRAM study. BMD was significantly lower in persons exposed to long-term passive smoking in their home during adulthood. Introduction Smoking is associated with decreased bone mineral density (BMD) and increased risk of osteoporotic fractures. This study aimed to investigate a possible association between BMD at the phalangeal bones and self-reported passive smoking. Methods The study included a cohort of 15,544 men and women aged 18-95 years, who underwent a BMD scan in the Danish KRAM study. BMD scans of the middle phalanges of the second, third and fourth digits of the non-dominant hand were performed with a compact radiographic absorptiometry system (Alara MetriScanA (R)). Also, height, weight and body fat percentage were measured and 96.7% (n = 15,038) of the participants answered a self-reported questionnaire with information on passive smoking, other lifestyle factors, education, etc. The association between passive smoking and BMD was examined using multiple linear regression analysis. Results A total of 39.1% (n = 5,829) of the participants had been exposed to passive smoking in adulthood at home. BMD was significantly lower in subjects exposed to passive smoking, 0.343 vs. 0.331 g/cm(2); p < 0.01 (unadjusted) and 0.339 vs. 0.337 g/cm(2); p < 0.05 (adjusted for age, gender, height and weight, and smoking). Multiple linear regression analysis showed that exposure to passive smoking for more than 20 years in adulthood at home was significantly related to BMD when adjusted for potential confounders (men, beta = -4.4 x 10(-3); r = -0.05; p < 0.01 and women, beta = -2.3 x 10 (-3); r = -0.03; p < 0.05). This relationship was also seen in the group of never smokers (beta = -3.3 x 10(-3); r = -0.03; p = 0.01). Conclusion Our study supports a potential negative effect of long-term passive smoking in adulthood at home on phalangeal BMD.