Low-Level Cadmium Exposure Is Associated With Decreased Bone Mineral Density and Increased Risk of Incident Fractures in Elderly Men: The MrOS Sweden Study.

Abstract

One risk factor for osteoporosis that has attracted increasing attention in recent years is exposure to cadmium. The aim of this study was to examine the associations between low-level cadmium exposure, from diet and smoking, and bone mineral density (BMD) and incident fractures in elderly men. The study population consisted of 936 men from the Swedish cohort of the Osteoporotic Fractures in Men (MrOS) study, aged 70 to 81 years at inclusion (years 2002 to 2004), with reliable data on cadmium in urine (U-Cd) analyzed using inductively coupled plasma mass spectrometry in baseline samples. The participants also answered a questionnaire on lifestyle factors and medical history. BMD was measured at baseline using dual-energy X-ray absorptiometry (DXA) in the total body, hip, and lumbar spine. During the follow-up period (until 2013), all new fractures were registered by date and type. Associations between BMD and U-Cd were assessed using multiple linear regression, and associations between incident fractures and baseline U-Cd were analyzed using Cox regression. In both cases, a number of potential confounders and other risk factors (eg, age, smoking, body mass index [BMI], and physical activity) were included in the models. We found significant negative associations between U-Cd and BMD, with lower BMD (4% to 8%) for all sites in the fourth quartile of U-Cd, using the first quartile as the reference. In addition, we found positive associations between U-Cd and incident fractures, especially nonvertebral osteoporosis fractures in the fourth quartile of U-Cd, with hazard ratios of 1.8 to 3.3 in the various models. U-Cd as a continuous variable was significantly associated with nonvertebral osteoporosis fractures (adjusted hazard ratio 1.3 to 1.4 per μg Cd/g creatinine), also in never-smokers, but not with the other fracture groups (all fractures, hip fractures, vertebral fractures, and other fractures). Our results indicate that even relatively low cadmium exposure through diet and smoking increases the risk of low BMD and osteoporosis-related fractures in elderly men.