Multivariate regression model showing the relationship between pack-years of smoking and the Bath Ankylosing Spondylitis Disease Activity Index in the patients with ankylosing spondylitis Model Regression 95% coefficients Confidence interval for B B Standard P Lower error boundary (Constant) 4.3 0.88 Less 2.49 than 0.001 Pack-years 0.05 0.02 0.05 0 Educational level -0.20 0.12 0.10 -0.43 Age at diagnosis 0.02 0.02 0.20 -0.01 (years)
Nephrolithiasis 1.02 0.54 0.06 -0.05 Psychiatric 0.87 0.38 0.02 0.12 comorbidities (depression) Model Upper boundary (Constant) 5.96 Pack-years 0.094 Educational level 0.04 Age at diagnosis 0.06 (years) Nephrolithiasis 2.09 Psychiatric 1.62 comorbidities (depression) B: Regression coefficient.