Are symptoms of insomnia in primary care associated with subsequent onset of dementia? A matched retrospective case-control study

Abstract

Objective: There is evidence from neuroimaging studies of an association between insomnia and early dementia biomarkers, but observational studies have so far failed to show a clear association between insomnia and the later development of dementia. We investigated the association between dementia diagnosis and recording of insomnia symptoms 5–10 years earlier in primary care.

Method: A case-control study using data from the Clinical Practice Research Datalink. 15,209 cases with dementia (either Alzheimer’s, vascular, mixed or non-specific subtypes) at least 65 years old at time of diagnosis, were matched with the same number of controls on year of birth and gender. We ascertained the presence of insomnia symptoms during a five-year period starting 10 years before the index date. Odds ratios for developing dementia were estimated using logistic regression after controlling for hypnotic exposure and physical and mental health comorbidities.

Results: The adjusted odds ratio for dementia in those with previous insomnia was 1.34 (95% CI = 1.20–1.50).

Conclusion: There is an association between dementia and previous insomnia. It may be possible to incorporate insomnia into predictive tools for dementia.

Keywords:

• Dementia
• insomnia
• sleep
• case–control study
• Clinical Practice Research Datalink (CPRD)
• primary care

Disclosure statement

All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf. and declare: support for the submitted work as described above; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work. NH reports personal fees and non-financial support from Rosch, grants and personal fees from Eli-Lily, and personal fees from GE Healthcare, all outside the submitted work. JC reports grants from NIHR and Wellcome Trust and other financial activities with BMJ Publishing and NHS Swale Clinical Commissioning Group, all outside the submitted work.

Data availability statement

Only the authors have access to the CPRD data. Codelists have been made available by the authors and deposited in the clinical codes repository (Hoile, 2019). Researchers should contact the CPRD’s Independent Scientific Advisory Committee (ISAC) to obtain access to data. The programming code used for data preparation and statistical analysis is available from the corresponding author’s Github repository (Hoile, 2018).

Ethical approval

Ethical approval was given by the CPRD Independent Scientific Advisory Committee (ISAC 17_057).

Additional information

Funding

This work was supported by funding from the Wellcome Trust (202133/Z/16/Z) and from the Brighton and Sussex Medical School Capital Expenditure Fund. The funders had no role in: the design and conduct of the study; in the collection, management, analysis, or interpretation of the data; nor in the preparation, review, or approval of this manuscript.