Figure 1. Mean differences (95%confidence intervals) in grip strength according to serum cotinine concentrations (ng/mL) based on restricted cubic splines with knots at the 10th, 50th, and 90th percentile of serum cotinine distribution. The reference value is set at the 25th percentile of the cadmium distribution. Models are adjusted for age, sex, race/ethnicity, education, place of birth, tobacco smoke, alcohol consumption, diet quality, physical activity, BMI, cardiovascular disease, respiratory disease, musculoskeletal disease, cancer, hypertension, diabetes and number of drug treatments. Lines represent predicted values (thick line) and 95% confidence intervals (dashed lines), and vertical bars represent the histogram of log-transformed serum cotinine distribution.