CRP and chronic obstructive pulmonary disease: Thus, this study did not consider hypnotic drug use, pro-inflammatory factors (e.g., CRP, interleukin-6), cortisol levels, sex hormones, and various diseases (e.g., obesity-hypoventilation syndrome, obstructive apnea, heart failure, chronic obstructive pulmonary disease, and cognitive impairment), all of which can affect sleep duration and frailty.