<b>Results</b>: Among the 62,714 patients, those receiving endocrine therapy had a higher risk of sleep disorders (hazard ratio [HR], 1.276; 95% confidence interval [CI], 1.087-1.497; <i>p</i> = 0.003), irrespective of tamoxifen or aromatase inhibitor use. This evidence concerns the gene CYP19A1 and sleep disorder.