RESET-BRAIN: REhabilitation of SleEp and CogniTive Impairment in BReast Cancer Survivors Using an App-based Intervention

The goal of the study is to investigate whether treating insomnia using app-based cognitive behavioral therapy for insomnia (CBT-I) can improve cognitive impairment in breast cancer survivors compared to an active control group (sleep hygiene education). The study will also explore if CBT-I is associated with changes in the brain and in inflammation. The investigators will recruit approximately 84 participants with insomnia and cognitive impairment who have completed breast cancer treatment within 1-5 years.

The study is a randomized controlled trial comparing the effect of app-based cognitive behavioral therapy for insomnia (CBT-I) on cognitive function and insomnia to an active control group (sleep hygiene). Participants will be 84 breast cancer survivors who have completed primary treatment within 1-5 years and experience insomnia and cognitive impairment. After baseline assessment, participants will be randomized to either app-based CBT-I or sleep hygiene (active control). Both groups will undergo post-treatment assessments and 6-months follow-up assessments. The primary outcomes will be cognitive impairment assessed with the Conners Continuous Performance Test (CCPT) and insomnia assessed with the Insomnia Severity Index (ISI). To explore potential neurobiological and inflammatory mechanisms, structural magnetic resonance imaging (MRI) and inflammatory markers will be secondary outcomes. To provide a broader insight into cognitive function, participants will undergo further neuropsychological assessment with various standardized neuropsychological tests.

The study has the following aims and hypotheses:

PRIMARY AIM: To investigate whether an app-based CBT-I is associated with improved sleep and cognitive function in BC survivors screened for insomnia and CI when compared with an active control group. PRIMARY HYPOTHESIS: Compared with an active control group, CBT-I will be associated with a statistically significantly greater reduction in insomnia severity using the ISI and improvement of sustained attention and executive function assessed objectively using the CCPT. Effects on secondary sleep outcomes will also be tested. Exploratory hypothesis: Improvements in sustained attention and executive function will be mediated by improved insomnia severity and sleep outcomes.

SECONDARY AIM 1: To investigate whether CBT-I is associated with altered structural brain outcomes when compared with an active control group. HYPOTHESIS: Compared with an active control group, CBT-I will be associated with changes in brain gray and white matter properties, structural network topology, as well as glymphatic function as operationalized with the diffusion tensor image along the perivascular space (DTI-ALPS) approach.

SECONDARY AIM 2: To explore whether CBT-I is associated with changes in inflammatory immune function (IL-1β, IL-6, TNF-α, IFN-γ) when compared with an active control group. HYPOTHESIS: Compared with an active control group, CBT-I will be associated with a statistically significantly greater reduction in inflammatory markers. Improvements in sustained attention and executive function will be mediated by changes in inflammatory markers.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥18 years
* Have completed primary breast cancer (BC) treatment within 1-5 years (endocrine therapies allowed)
* Insomnia: a score of \>10 on the Insomnia Severity index (ISI) and/or meet the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria for Insomnia Disorder
* Cognitive impairment: a score of "quite a bit" or "very much" on at least 1 of the 2 items measuring concentration and memory on The European Organization for Research and Treatment of Cancer Core Quality of Life (EORCT-QLQ-C30) and/or \<54 on the Cancer Therapy-Cognitive (FACT-Cog) perceived cognitive impairment (PCI) subscale

Exclusion Criteria:

* Other sleep disorders than insomnia that may confound sleep and/or cognitive function
* Use of drugs impacting that may confound sleep and/or cognitive function (endocrine therapies allowed)
* Neurodegenerative and psychiatric disorders that may confound sleep and/or cognitive function
* Shift work
* Pregnancy or maternity leave
* Recurrence of BC or new cancer
* Insufficient Danish proficiency
* Substance abuse that may confound sleep and/or cognitive function
* Previous experience with CBT-I
* Other cancer than breast cancer