Genetic analysis links insomnia liability to higher inflammation marker C-reactive protein, suggesting sleep problems may drive systemic inflammation rather than simply correlate with it.
A team from Massachusetts General Hospital and the Broad Institute discovered 125 genetic locations linked to both insomnia and raised C-reactive protein (CRP), a sign of mild inflammation. Analyzing UK Biobank records, they compared 130,611 people with insomnia symptoms against 327,375 without. After accounting for age, sex, and genetic background, those with insomnia showed higher CRP levels—a trend that held even when excluding individuals with mental health conditions, chronic illnesses, sleep medications, or irregular work schedules (average increase: 0.077 mg/L).
Genetic Correlation Supports Causal Direction
Genome-wide analyses revealed a positive genetic correlation of 0.186 between insomnia and CRP, indicating modest overlap in genetic influences on both traits. Mendelian randomization analysis showed genetic liability to insomnia was associated with higher CRP levels (inverse variance weighted β = 0.299; P = 5.52 × 10⁻¹⁰), with weighted median, weighted mode, and simple mode estimates all agreeing. The reverse analysis was less consistent, with CRP as the exposure producing only a small positive estimate that showed evidence of directional pleiotropy.
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Further testing confirmed six genetic regions near APOE, HLA-B, NLGN1, AK5/DNAJB4, FAM114A2/GRIA1, and SATB1 likely influence both insomnia and CRP. The APOE area showed almost perfect overlap (probability: 0.9997). Interestingly, the APOE ε4 variant, known to increase Alzheimer’s risk, was tied to lower odds of insomnia and reduced CRP, hinting at complex interactions in brain immunity.
The genes at these shared locations were strongly tied to immune responses and stress pathways, such as interferon signaling and inflammation via NF-κB. They also played roles in DNA packaging and protein assembly, particularly in brain areas like the hypothalamus, midbrain, and thalamus.
Biological Mechanisms and Sex Differences
Within the healthy subgroup, the CRP association was stronger in women than in men and peaked among participants aged 39 to 50 years before declining in older groups. A pleiotropy analysis found only 67 variants (53.6%) had the same effect direction for both traits, a proportion not statistically significant. The insomnia data came from a meta-analysis of 593,724 cases and 1,771,286 controls.
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This genetic evidence aligns with previous studies showing that insomnia sufferers have higher inflammatory markers, but the new analysis provides mechanistic insight into how genetic factors may link the two conditions. The finding that APOE ε4 associates with both lower insomnia risk and lower CRP suggests complex neuroimmune interactions that differ from typical expectations given Alzheimer’s disease associations.
Limitations and Future Research
Because insomnia was self-reported, some overlap in genetic influences couldn’t be ruled out entirely. The study relied on European ancestry groups, and gender-specific analyses missed data from 23andMe, limiting their precision. The researchers urged further studies to see if better sleep reduces CRP and to explore the biological role of these genetic regions, especially APOE.
“Targeting pathways involved in neuroimmune signaling, glial function, and synaptic regulation may offer strategies to mitigate the inflammatory consequences of sleep disruption,” the authors wrote. “Incorporating genetic information could further enable the development of individualized approaches aimed at improving sleep while reducing systemic inflammatory burden.”