ACUTE BLOOD-PRESSURE ELEVATIONS WITH CAFFEINE IN MEN WITH BORDERLINE SYSTEMIC HYPERTENSION

Whether the vasoconstrictive actions of caffeine are enhanced in hyper tensive persons has not been demonstrated, Thus caffeine 13.3 mg/kg) v ersus placebo was tested in 48 healthy men (aged 20 to 35 years) selec ted after screening on 2 separate occasions. Borderline hypertensive m en (n = 24) were selected with screening systolic blood pressure (BP) of 140 to 160 mm Ha and/or diastolic BP 90 to 99 mm Hg. Low-risk contr ols In = 24) reported no parental history of hypertension and had scre ening BP <130/85 mm Hg. Participants were then tested on 2 occasions a fter 12-hour abstinence from caffeine in each of 2 protocols; this req uired a total of 4 laboratory visits. Caffeine-induced changes in dias tolic BP were 2 to 3 times larger in borderline subjects than in contr ols (+8.4 vs +3.8 mm Hg, p <0.0001), and were attributable to larger c hanges in impedance-derived measures of systemic vascular resistance ( +135 vs +45 dynes . s . cm(-5), p <0.004). These findings were consist ent and reached significance in both protocols. The percentage of bord erline subjects in whom diastolic BP changes exceeded the median contr ol response was 96%, Consequently whereas all participants exhibited n ormotensive levels during the resting predrug baseline, 33% of borderl ine subjects achieved hypertensive BP levels after caffeine ingestion, Thus, in borderline hypertensive men, exaggerated responses to caffei ne were: selective for diastolic BP, consistent with greater vasoconst riction, replicated in 2 protocols, and representative of nearly all b orderline hypertensives, We suspect that the potential far caffeine to stabilize high resistance states in susceptible persons suggests that its use may facilitate their disease progression, as well as hinder a ccurate diagnosis and treatment.