ARTERIAL BARORECEPTOR-CARDIAC REFLEX SENSITIVITY IN THE ELDERLY

Uncertainty still remains regarding the differing effects of blood pre ssure and age on baroreceptor-cardiac reflex sensitivity in elderly in dividuals; these differences are at least partly due to the differing methods and subject groups used in previous studies. We sought to reso lve these issues by examining baroreflex sensitivity in 54 subjects ag ed 70 +/- 1 years (mean +/- SE; range, 60 to 81) divided into groups w ith combined systolic diastolic hypertension (CH group, n = 16), isola ted systolic hypertension (ISH group, n = 16), or normotension (NT gro up, n = 22). Baroreflex sensitivity was quantified from the pulse inte rval and blood pressure responses to the Valsalva maneuver and presser (phenylephrine) and depressor (sodium nitroprusside) stimuli. Baroref lex sensitivity was significantly reduced in the two hypertensive grou ps but did not differ between them (Valsalva maneuver: CH group, 1.9 /- 0.3 ms/mm Hg; ISH group, 2.8 +/- 0.5; NT group, 4.4 +/- 0.4; phenyl ephrine: CH group, 3.1 +/- 0.6; ISH group, 3.5 +/- 0.7; NT group, 7.7 +/- 1.0; sodium nitroprusside: CH group, 2.1 +/- 0.3; ISH group, 3.6 /- 0.8; NT group, 5.4 +/- 0.3; all P < .05 for comparison with the NT group). Thus, this study demonstrated reductions in baroreflex sensiti vity with hypertension in elderly subjects consistent across all metho ds but with no difference between subjects with combined hypertension and isolated systolic hypertension matched for similar systolic pressu re. Baroreflex sensitivity was related only to the level of systolic p ressure independent of diastolic pressure or age. If elderly subjects with isolated systolic hypertension have a greater reduction in large- artery compliance than combined hypertensive subjects with similar sys tolic pressure, this does not appear to lead to further reductions in baroreflex sensitivity in these individuals.