['Obstructive sleep apnea syndrome (OSAS) is associated with long-term cardiovascular morbidity. Little is known about these relations at early stages. We conducted a case-control study in which we analyzed the clinical characteristics of young adults who underwent a periodic health examination and were screened for, and eventually found to experience, OSAS.', 'We identified 121 subjects newly diagnosed in a sleep study as having OSAS, and 229 matched control subjects in which screening for OSAS was negative. All had a medical interview, physical examination, and routine laboratory tests.', 'Subjects who had OSAS had a higher, body mass index (3-kg/m(2) difference) and a higher diastolic blood pressure (4-mm Hg difference) value, without elevation in systolic blood pressure. There was no metabolic difference (lipids profile and fasting glucose levels) between groups.'] Is diastolic blood pressure the first to rise in association with early subclinical obstructive sleep apnea : lessons from periodic examination screening?