Which came first, obstructive sleep apnea or hypertension? A retrospective study of electronic records over 10 years, with separation by sex

Objectives: Obstructive sleep apnea (OSA) is a risk factor for hypertension (HTN), but the clinical progression of the sleep disorder to the high blood pressure condition is unclear. There are also sex differences in prevalence, screening and symptoms of OSA. The objective was to estimate the time from OSA to HTN diagnoses, with sex-specific quantification. Design: Retrospective analysis of electronic health records (EHR) over a 10-year period (2006 to 2015 inclusive). Setting: UCLA Health System in Los Angeles, California, USA. Participants: 4848 patients: female N=2086, mean [age{+/-}std] = 52.8{+/-}13.2 years; male N=2762, age=53.8{+/-}13.5 years. These patients were selected from 1.6 million patients with diagnoses in the EHR who met the criteria of: diagnoses of OSA and HTN; in long-term care defined by ambulatory visits at least one year prior and one year subsequent to the first OSA diagnosis; no diagnosis of OSA or HTN at intake; and a sleep study performed at UCLA. Primary and secondary outcome measures: The primary outcome measure in each patient was time from the first diagnosis of OSA to the first diagnosis of HTN (in days). Since HTN and OSA are progressive disorders, a secondary measure was relationship between OSA-to-HTN time and age. Results: The mean, std and 95% confidence intervals of the time from OSA to HTN diagnoses were: all -732 {+/-} 1094.9 [-764.6, -701.8] days; female -815.9 {+/-} 1127.3 [-867.3, -764.2] days; and male -668.6 {+/-} 1065.6 [-708.1, -626.8] days. Age was negatively related to time from OSA to HTN diagnosis in both sexes. Conclusions: HTN was on average diagnosed years prior to OSA, with a longer separation in females. Our findings suggest under-screening of OSA, more so in females than males. Undiagnosed OSA may delay treatment for the sleep disorder and perhaps affect the development and progression of HTN.