No effect of stage 1 hypertension or hypertensive medication on critical environmental limits (PSU HEAT Project)

Middle-aged and older individuals with hypertension are often considered to be at increased risk during environmental heat waves due to blunted increases in skin blood flow and subsequently elevated core temperatures. In addition, common antihypertensive medications [i.e., angiotensin-converting enzyme (ACE) inhibitors, diuretics, and b blockers] can independently impair heat loss mechanisms, reportedly heightening heat-related risk. If these groups are at increased risk, differences should be observed in the environmental conditions in which thermal balance can occur. Identifying critical environmental limits is an integrative method to determine the conditions that separate safe from unsafe heat exposure. Seventy-two participants (F = 43) (63 ± 11 yr; range: 40–92 yr) were exposed to progressive heat stress at a low metabolic rate. Thirty-seven of the participants were hypertensive [defined by current American Heart Association (AHA) guidelines for stage 1 hypertension] and 15 participants were taking antihypertensive medications. Experiments were conducted in both hot-dry [(HD); up to 53^ͦC, ≤25% relative humidity (rh)] and warm-humid (WH; ~35^ͦC, ≥50% rh) environments. One-way ANOVA was used to compare normotensives with hypertensive individuals with and without the use of antihypertensive medications in the WH environment. Unpaired t tests were used to compare differences between hypertensives and normotensives in the HD environment. No differences in critical environmental limits were observed in either environment among all groups (all P > 0.05). These data challenge the hypotheses that hypertension increases heat-related risk. Despite potential alterations in heat loss mechanisms due to hypertension and antihypertensive medications, there were not differences in the compensable environmental conditions in individuals with stage 1 hypertension.