Correlations of Age, BMI, and MBD to high and low % collagen. Each characteristic was fit as an independent variable with as the dependent variable using Pearson’s correlations and linear fits to establish relationships. Age and BMI were found to be independently associated with . decreased with both age and BMI but exhibited a stronger negative relationship to age in sites with a high percentage of collagen. MBD was positively correlated with but not independent of age and BMI.