Abstract
Reduced cardiorespiratory fitness (CRF) is the hallmark symptom of heart failure with preserved ejection fraction (HFpEF). Sleeping disorders are common in patients with HFpEF, however is unknown if this contributes to impaired CRF. We investigated the effects of sleep quality on CRF in HFpEF. We hypothesized that sleep disruption would be associated with lower CRF.
In this cross-sectional analysis of patients with HFpEF, we objectively measured sleep quality using a tri-axial wrist activity monitor (GT9X Link, ActiGraph, FL), using a 24 hour wear protocol for 7 consecutive days, except when bathing and/or swimming. Sleep periods were detected with a modified Tudor-Locke algorithm and scored via the Cole-Kripke algorithm using ActiLife software (v. 6.13.4). Participants without 3 days of ≥1,200 minutes of wear time were excluded from the analysis. To evaluate sleep quality, we assessed sleep efficiency, wake after sleep onset (WASO), number of wakening, wakening lengths (WASO), movement index during sleep, fragmentation index, and sleep fragmentation index. A conservative ramping, maximal effort cardiopulmonary exercise test was performed on a treadmill to determine VO2peak as a measure of CRF. We compared VO2peak and exercise time between below-median vs above-median in all sleep variables using Man-Whitney U test. Spearman's rank tests were used to assess correlations between sleep outcomes and CRF outcomes. Data are presented as median [IQR].
Thirteen patients were included in this analysis (Mean [IQR], Age 64 [52-73] years; body mass index (BMI): [31.8-41.7] 35.6 kg/m2). Patients were predominantly female (92%), 53.8% had diabetes, 92.3% had hypertension and 31% had sleep disorders (sleep disorders breathing). Actigraph wear time was 166.5 [141.7-168] hours. VO2 peak was 16.7 [14.6-18.4] mL•kg−1•min−1. Patients with worse sleep quality defined as having a lower sleep efficiency, higher WASO, and greater movement index had lower VO2peak compared to those with higher sleep quality (Figure 1). Movement index during sleep (r=-0.698, p=0.008) and length of awakening (r=-0.676, p=0.011) negatively correlated with peak VO2, while sleep efficiency (r=0.527, p=0.064), WASO (r=-0.533, p=0.061) presented a trend for association with VO2peak.
Objectively measured poor sleep quality correlated with reduced CRF in HFpEF. Future studies investigating the underlying mechanisms of this association and potential interventions targeting sleep quality to improve CRF in HFpEF are warranted.