Exploration of effects of galvanic vestibular stimulation on circadian rhythms and its associations with sleep and spatial memory in patients with breast cancer: The ICANSLEEP-2 protocol

Abstract

Background: Patients with breast cancer (BC) exhibit circadian rhythm disruptions, mainly of rest-activity rhythm (RAR), of which sleep is an essential component, and cortisol rhythm. Sleep complaints such as insomnia and cognitive impairments are prevalent in BC. In general population, sleep is known to contribute greatly to cognition. Thus, improving RAR (and particularly sleep) could help limiting cognitive impairments in BC patients. It has recently been suggested that, in addition to its essential role in spatial memory, the vestibular system contributes to RAR synchronization. Its stimulation could therefore limit both sleep disturbances and spatial memory deficits in BC.

Objectives: The main aim of the ICANSLEEP-2 study is to assess the effects of galvanic vestibular stimulation (GVS) on circadian rhythms. The secondary aim is to assess whether GVS improves sleep and spatial memory in BC patients.

Methods: Two groups with insomnia complaints (Insomnia Severity Index > 7) will be included: a patients' group with BC (n = 50) and a healthy control group without history of cancer (n = 25). There will be two assessment sessions, before and after 2 weeks of GVS. Patients will be randomly assigned to either a GVS group or a sham group (noneffective stimulation). Controls will receive GVS. GVS effects will be quantified and compared between groups. Assessments will include actigraphy, salivary cortisol, polysomnography, a cognitive test battery (including a computer-based task for spatial memory) and validated questionnaires (for psychological functioning and sleep complaints).

Discussion: Current methods for improving sleep in BC have had controversial outcomes regarding sleep structure. We expect GVS to offer a new mean of directly targeting RAR disruptions in BC patients, with beneficial effects on sleep structure. Given the crucial impact of sleep on cognitive functioning, notably spatial memory, improving sleep of BC patients should enhance their cognitive functioning.

Ethics and dissemination: This study received ethical approval from the Ile de France IV institutional review board on 19 April 2022 (no. ID-RCB: 2022-A00437-36). The findings yielded by this protocol will be presented at various conferences and in peer-reviewed journals.

Clinicaltrials.gov registration number: NCT05414357.

Fig 1. ICANSLEEP-2 trial design.

Fig 2. General design of spatial memory task (adapted from Hilliard et al., 2019).

Computer-based spatial memory task. Task performed on two successive days and featuring three distinct phases. On Day 1, all three phases will take place. On Day 2, only Phases B and C will take place. A: first phase; B: second phase; C: third phase. A: Participant’s point of view. Participants have to collect objects in the arena. B: Top view. Participants have to put back the objects they collected. C: Top view. Participants have to put back the objects they collected in a modified environment. This modification will consist of either the movement of an intra-labyrinthic cue (plot) or an enlargement of the perimeter wall.

Fig 3. GVS device.

1. GVS generator. The device delivers the electrical current based on the parameters entered beforehand by the experimenter. 2. Headband. This plastic strip is put on the participant’s head with an arrow pointing to the forehead. 3: Sponges. Sponges containing electrodes. These sponges have to be clipped to the bottom of the headband. They allow the current to be delivered behind the ears.