{
  "abstract": "Background Sleep restriction and irregular sleep are common in older adults and can impair cardiac autonomic function. However, it remains unclear how recovery sleep and sex moderate these effects. We examined nocturnal heart rate variability (HRV) from baseline to recovery following sleep restriction or scheduled napping in healthy older adults.Method Thirty-eight individuals (mean±SD age, 64.9±9.0 years; 47% male) completed a 2.5-day laboratory protocol. After baseline polysomnography, participants were assigned to either a 40-hour sleep deprivation or a multinap protocol, followed by a recovery night.HRV was assessed in continuous 5-minute segments during N2, N3, REM on both nights. Parameters included low frequency (LF), high frequency (HF), LF/HF ratio, standard deviation of NN-intervals (SDNN), and root mean square of successive RR-interval differences (RMSSD).Wilcoxon signed-rank tests compared HRV across sleep stages and nights in the full sample and by sex. HRV recovery-to-baseline ratios were entered into general linear models (GLMs) to assess effects of condition, sex, and their interaction, for each parameter and stage.Results HRV varied significantly across sleep stages (except SDNN). RMSSD (23.2±11.5ms) and HF (20.1±11.2ms 2) were significantly lower, and LF (62.2±14.3ms2) and LF/HF (5.47±3.96) were higher, in REM compared with N2 and N3 (p<0.01). Stage-related HRV differences were seen in both sexes, with stronger effects in women.GLMs of HRV ratios revealed significant protocol and sex interactions across all parameters except SDNN, indicating sex-specific recovery responses. In N2, LF/HF showed a significant interaction: F(1)=6.50, p=0.016, partial η2=0.178. Women exhibited a more pronounced increase in LF/HF following sleep deprivation.Conclusion REM was marked by reduced parasympathetic activity, compared to other stages, particularly in women. Recovery sleep modulated HRV in a sex and protocol-dependent manner, with the strongest effects in N2. These findings highlight the complex interplay between sleep stage and sex in shaping autonomic recovery following sleep restriction.",
  "authors": [
    {
      "affiliations": [
        "Faculty of Medicine and Health Sciences, University of East Anglia, Norwich, United Kingdom"
      ],
      "name": "Bindiya Shenoy"
    },
    {
      "affiliations": [
        "Faculty of Medicine and Health Sciences, University of East Anglia, Norwich, United Kingdom",
        "Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy"
      ],
      "name": "Adriana Michalak"
    },
    {
      "affiliations": [
        "Faculty of Medicine and Health Sciences, University of East Anglia, Norwich, United Kingdom"
      ],
      "name": "Molly Scoble"
    },
    {
      "affiliations": [
        "Faculty of Medicine and Health Sciences, University of East Anglia, Norwich, United Kingdom"
      ],
      "name": "Ziad Shabana"
    },
    {
      "affiliations": [
        "Faculty of Medicine and Health Sciences, University of East Anglia, Norwich, United Kingdom"
      ],
      "name": "Michael Hornberger"
    },
    {
      "affiliations": [
        "Faculty of Medicine and Health Sciences, University of East Anglia, Norwich, United Kingdom"
      ],
      "name": "Alpar S Lazar"
    }
  ],
  "title": "O26 Sex differences in nocturnal autonomic recovery following sleep restriction in healthy older adults",
  "uid": "fd9c1085-1f74-5a42-85e5-27258f3e3417"
}