Chronobiological characterization of women with primary vasospastic syndrome: body heat loss capacity in relation to sleep initiation and phase of entrainment

Abstract

Women with primary vasospastic syndrome (VS), but otherwise healthy, exhibit a functional disorder of vascular regulation (main symptom: cold extremities) and often suffer from difficulties initiating sleep (DIS). Diverse studies have shown a close association between distal vasodilatation before lights off and a rapid onset of sleep. Therefore, we hypothesized that DIS in women with VS could be due to a reduced heat loss capacity in the evening, i.e., subjects are physiologically not ready for sleep. The aim of the study was to elucidate whether women having both VS and DIS (WVD) or not (controls) show different circadian characteristics (e.g., phase delay of the circadian thermoregulatory system with respect to the sleep-wake cycle). Healthy young women ( n = 9 WVD and n = 9 control) completed a 40-h constant routine protocol (adjusted to habitual bedtime) before and after an 8-h sleep episode. Skin temperatures [off-line calculated as distal-proximal skin temperature gradient (DPG)] and core body temperature (CBT; rectal) were continuously recorded. Half-hourly saliva samples were collected for melatonin assay and subjective sleepiness was assessed on the Karolinska Sleepiness Scale (KSS). Compared with control, WVD showed no differences in habitual bed times, but a 1-h circadian phase delay of dim light-melatonin onset (hours after lights on: WVD 14.6 ± 0.3 h; control 13.5 ± 0.2 h; P = 0.01). Similar phase shifts were observed in CBT, DPG, and KSS ratings. In conclusion, WVD exhibit a phase delay of the endogenous circadian system with respect to their habitual sleep-wake cycle, which could be a cause of DIS.

Predominance of Distal Skin Temperature Changes at Sleep Onset across Menstrual and Circadian Phases

“…Nevertheless, women undergoing a CR during LP showed peak DPG near the middle of their projected habitual nocturnal sleep episode (Vollenweider et al, 2008), which is similar to our results.…”

“…Current cross-correlations lend indirect support to the hypothesis that nocturnal sleep initiation mechanisms are likely triggered by a thermoregulatory cascade involving the onset of endogenous melatonin secretion . While we would expect melatonin increases to also precede DT/DCG increases, our finding of a nonsignificantly phase-advanced melatonin rhythm relative to DCG agrees with results of a study that also failed to detect significant phase lags between the 2 parameters (Vollenweider et al, 2008). Nonetheless, manipulation of this system via administration of exogenous melatonin during the daytime when endogenous melatonin is low elicits the characteristic changes associated with opening the "sleep gate" (Lavie, 1986), including increased peripheral heat loss (Krauchi et al, 1997), decreased CBT (Krauchi et al, 1997), and increased subjective (Cajochen et al, 1996;Krauchi et al, 1997) and objective (Cajochen et al, 1996) sleepiness.…”

“…This formed the basis of an experimental approach that employed a wearable thermosuit to alter skin temperature and was successful in promoting sleep (Raymann et al, 2005). A similar nonpharmacological approach can be used in females with sleep complaints, particularly in those with vasospastic syndrome who experience impaired heat loss mechanisms (Vollenweider et al, 2008).…”

“…Namely, while the lights-off-induced increases in DT are not eliminating menstrual phase differences in CBT, they do seem to be sufficient to maintain comparable circadian sleep propensity across the menstrual cycle. Women with an altered vasodilatory response or thermoregulatory heat loss system may therefore become susceptible to sleep onset complaints (Vollenweider et al, 2008).…”

Thermal discomfort with cold extremities in relation to age, gender, and body mass index in a random sample of a Swiss urban population

“…PVD subjects suffer more intensely from cold hands and feet (TDCE) [30,31]. These people also tend to have a low BMI.…”