The influence of the Brinkman index on bone mineral density

Abstract<br> Background and purpose: Recently, as the Japanese population ages, the prevention of locomotive syndrome is garnering attention regarding the extension of health span. Osteoporosis is one of the main causes for locomotive syndrome, and prevention and early detection efforts are becoming increasingly important issues. Smoking is thought to be one of the lifestyle-induced causes of osteoporosis. Many studies indicate a significant decrease of bone mineral density along with a significant increase in the risk of fracture in smokers, but the relationship between the Brinkman index (cigarettes/day times years of smoking) and bone mineral density has not been elucidated upon. Therefore, we studied the relationship between the Brinkman index and bone mineral density in women, as well as evaluated the risk of bone mineral density loss from smoking.<br> Subject and methods: This cross-sectional study targeted both current and past female smokers. Females who received a bone mineral density examination during a medical checkup at Kawasaki Medical University Hospital between April 1, 2008 and March 31, 2017 were enrolled in this study. We excluded those without any data about their smoking history. After the exclusions, 328 females were included in the study. Patient age, BMI, menopausal status, Ca, IP, HbA1c, eGFR, Alb, Brinkman index, and bone mineral density were all taken from the medical checkup data. Bone mineral density was defined as a T-score of the lumbar spine and femoral neck measured by DXA. Laboratory data from smokers and ex-smokers were compared and the association between T-score and Brinkman index was assessed via multiple regression analysis.<br> Results: Of the 328 females, 19 were current smokers and 16 were ex-smokers. The current age of current smokers was 49.9 +/- 11.7 years old, with a BMI of 20.5 +/- 3.8 kg/m2. The ex-smokers were 51.4 +/- 9.6 years old, with a BMI of 20.4 +/- 2.9 kg/m2. After a multiple regression analysis, the partial regression coefficient of the Brinkman index and lumbar spine T-score was -0.65 (p=0.01), and there was a significant negative association between the Brinkman index and lumbar spine T-score in the women. The partial regression coefficient of the Brinkman index and the femoral neck T-score was -0.43 (p=0.06), which was not significant but showed some relevance.<br> Conclusions: In the females in this study, there was a significant negative relationship between the Brinkman index and lumbar spine bone mineral density, along with some tendency observed at the femoral neck. This relationship shows that a patient’s cumulative tobacco usage can be an important health indicator, regardless of or in addition to current usage. Of course, patients should be advised to cease smoking, and patients with a high cumulative tobacco usage should be advised to have a bone mineral density test.