{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T03:56:45Z","timestamp":1790740605072,"version":"4.1.0"},"reference-count":44,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"22","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["JAHA"],"published-print":{"date-parts":[[2025,11,18]]},"abstract":"<jats:sec xml:lang=\"en\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p xml:lang=\"en\">In people with obstructive sleep apnea (OSA), adverse cardiovascular events, such as myocardial infarction, occur more commonly in the middle of the night than at other times of the day. These events could occur as a result of the nighttime physiological changes in OSA, but the endogenous circadian system has been implicated in increased cardiovascular risk in OSA. Vascular endothelial function is a marker of prospective cardiovascular risk and is impaired in OSA. We hypothesized that the nighttime risk in OSA could be due to a circadian system\u2013driven nighttime impairment in vascular endothelial function.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec xml:lang=\"en\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p xml:lang=\"en\">Twelve adults (healthy except for untreated moderate to severe OSA, 8 men and 4 women, 51\u00b1 SD 7\u2009years; apnea\/hypopnea index, 29\u00b119 hours of sleep) completed a 5\u2010day circadian protocol consisting of 10 recurring 5\u2010hour 20\u2010minute periods (2\u2009hours 40\u2009minutes each of wake periods and sleep opportunities) to separate the circadian system\u2019s effects from those of behaviors such as exercise, meal intake, and sleep. We measured flow\u2010mediated dilation of the brachial artery during each wake period in each participant.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec xml:lang=\"en\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p xml:lang=\"en\">\n                      We discovered a significant circadian rhythm in flow\u2010mediated dilation (\n                      <jats:italic toggle=\"no\">P<\/jats:italic>\n                      =0.019), and flow\u2010mediated dilation normalized to shear rate (\n                      <jats:italic toggle=\"no\">P<\/jats:italic>\n                      =0.037) with a trough at the circadian phase corresponding to \u22483:00\u2009\n                      <jats:sc>am<\/jats:sc>\n                      with a peak\u2010to\u2010trough change of 2.5 percentage points, or 82%. There was no significant circadian rhythm in the baseline diameter (\n                      <jats:italic toggle=\"no\">P<\/jats:italic>\n                      =0.39).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec xml:lang=\"en\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p xml:lang=\"en\">These data suggest that the circadian system impairs vascular endothelial function during the biological night, potentially increasing vascular vulnerability in people with untreated OSA.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec xml:lang=\"en\">\n                    <jats:title>Registration<\/jats:title>\n                    <jats:p xml:lang=\"en\">\n                      URL:\n                      <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"uri\" xlink:href=\"https:\/\/clinicaltrials.gov\/study\/NCT02202811\">https:\/\/clinicaltrials.gov\/<\/jats:ext-link>\n                      ; Unique Identifier: NCT02202811.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1161\/jaha.125.043596","type":"journal-article","created":{"date-parts":[[2025,11,6]],"date-time":"2025-11-06T12:04:59Z","timestamp":1762430699000},"update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":2,"title":["Endogenous Circadian System Attenuates Nighttime Vascular Endothelial Function in People With Untreated Obstructive Sleep Apnea"],"prefix":"10.1161","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5075-4340","authenticated-orcid":false,"given":"Saurabh S.","family":"Thosar","sequence":"first","affiliation":[{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Oregon Health and Science University","place":["Portland, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3729-7082","authenticated-orcid":false,"given":"Nicole P.","family":"Bowles","sequence":"additional","affiliation":[{"name":"Oregon Health and Science University","place":["Portland, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0229-3199","authenticated-orcid":false,"given":"Matthew P.","family":"Butler","sequence":"additional","affiliation":[{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Oregon Health and Science University","place":["Portland, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9428-6884","authenticated-orcid":false,"given":"Andrew W.","family":"McHill","sequence":"additional","affiliation":[{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Oregon Health and Science University","place":["Portland, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7712-4667","authenticated-orcid":false,"given":"Sean P.M.","family":"Rice","sequence":"additional","affiliation":[{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Oregon Health and Science University","place":["Portland, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2156-6340","authenticated-orcid":false,"given":"Jonathan S.","family":"Emens","sequence":"additional","affiliation":[{"name":"Oregon Health and Science University","place":["Portland, USA"]},{"name":"Portland VA Medical Center","place":["Portland, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1949-0954","authenticated-orcid":false,"given":"Steven 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