Increased blood cadmium levels were not associated with increased fracture risk but with increased total mortality in women: the Malmö Diet and Cancer Study

SUMMARY: This study aimed to investigate if high levels of blood cadmium at baseline were associated with increased fracture risk during follow-up in middle-aged women. No increased fracture risk was observed during follow-up, but women with higher levels of cadmium had an increased overall mortality. INTRODUCTION: Exposure to high levels of cadmium has been associated with an increased fracture risk. The aim was to investigate a perceived association between low levels of blood cadmium (B-Cd) at baseline and risk of first incident fracture. METHODS: From the population-based Malmö Diet and Cancer Study Cardiovascular cohort, 2920 middle-aged women with available background questionnaire and B-Cd measurements were included. Women were divided into quartiles (Q) according to their cadmium levels (Cd-Q1 <0.18 μg/L, Cd-Q2 0.18–0.28 μg/L, Cd-Q3 0.28–0.51 μg/L, and Cd-Q4 >0.51 μg/L). National registries were analysed for prospective risk of fractures or death. Associations between B-Cd and fracture risk were assessed by survival analysis (Cox regression analysis). RESULTS: In total, 998 first incident fractures occurred in women during a follow-up lasting 20.2 years (median) (12.5–21.2 years) (25th–75th percentile). Women in Cd-Q4 were more often current smokers than in Cd-Q1 78.4 vs. 3.3% (p < 0.001) and the number of cigarettes smoked per day correlated with B-Cd (r = 0.49; p < 0.001). The risk of fracture was not associated with baseline B-Cd in adjusted models. The hazard ratio (HR) Cd-Q4 vs. Cd-Q1 was 1.06 (95% confidence interval (CI) 0.89–1.27). In the multivariate Cox regression, independent variables for increased fracture risk were history of gastric ulcer and increasing age, whereas increasing body mass index (BMI) lowered fracture risk. Overall mortality was significantly higher for women with high B-Cd, HR 2.06 (95% CI 1.57–2.69). CONCLUSIONS: Higher blood levels of cadmium did not increase fracture risk in middle-aged women but reduced overall survival.