Comparison of acute effects of inspiratory muscle strength training between older adults with and without obstructive sleep apnea

Background: Inspiratory muscle strength training (IMST) has attracted much attention in the intervention for hypertension in individuals with obstructive sleep apnea (OSA). In individuals with OSA, chronically elevated muscle sympathetic nerve activity (MSNA) may increase systemic vascular resistance (SVR), potentially leading to elevated resting blood pressure. To address this issue, a long-term IMST program (30 training breaths/day, 5 days/wk for 6 wk) has been reported effectively lower to mean arterial pressure (MAP) in older adults with OSA. However, the acute effects of IMST on MAP in individuals with OSA were unexplored, and thus the underlying mechanism is not fully understood. In young healthy adults, acute IMST has been shown to lower muscle sympathetic nerve activity (MSNA). This IMST-induced decrease in MSNA is presumably due to the repetitive increase in venous return, which inhibits sympathetic outflow via cardiopulmonary receptors. While it remains unclear whether the cardiopulmonary reflex is maintained in older adults with OSA compared to age-matched controls, it is assumed to be relatively preserved in older adults with OSA without cardiac hypertrophy. Purpose: This study aimed to elucidate whether there are differences in acute effects of IMST on SVR and BP between older adults with OSA and their age-matched counterparts. We hypothesized that a single session of IMST may lead comparable reductions in SVR in older adults with OSA compared to those without OSA. Methods: Eleven older adults with OSA (OSA; 9M/2F, 64 ± 8 yrs, mean ± SD) undergoing continuous positive airway pressure treatment and 7 adults without OSA (CON; 4M/3F, 65 ± 6 yrs) were studied. Following 3 minutes of rest, subjects performed 30 breaths per session (6 breaths/set, 5 sets) of IMST at 50–60% of maximal inspiratory pressure, with 2-minute intervals between sets. Beat-by-beat changes in systolic and diastolic BP (SBP and DBP, respectively), and CO were recorded continuously before and during IMST. SVR was calculated as MAP/CO. BPs, CO, and SVR were assessed by comparing the mean values from 30 seconds before IMST to those during the 3rd, 4th, and 5th sets of IMST and the percent change from baseline was also calculated. Results: In both groups, IMST reduced DBP and SVR, and increased CO (P < 0.01). SBP significantly decreased by IMST only in the OSA group (P < 0.01). The percent change in CO during IMST was lower in the OSA group compared to the CON group (P = 0.046), whereas the percent change in SVR showed no significant difference (P = 0.43). Conclusion: As we expected, the IMST-induced reduction in SVR was similar between groups. The effects of IMST on SVR were comparable between the groups; however, the OSA group exhibited a smaller increase in CO and a more pronounced reduction in MAP compared to age-matched control subjects. This study was supported by JSPS KAKENHI #21K11170 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.