Insomnia Symptoms Weakly Associated with Increased Risk of Bloodstream Infection

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Individuals who reported three cumulative insomnia symptoms of DIS, DSM and NRS had 40% increased risk of future bloodstream infection.

Frequent insomnia and insomnia symptoms were associated with a weak positive increased risk of bloodstream infection (BSI) compared with those reporting no symptoms in new findings from Norway.

Individuals who reported three cumulative insomnia symptoms of “difficulty initiating sleep” (DIS), “difficulties maintaining sleep” (DMS), and “non-restorative sleep” (NRS) had a 40% increased risk of future BSI.

“As BSI is a global concern, addressing modifiable risk factors such as insomnia is of utmost importance to reduce the burden of BSI,” wrote study author Marianne S. Thorkildsen, Gemini Center for Sepsis Research at Institute of Circulation and Medical Imaging.

Insomnia has been previously linked to decreased immune function and increased risk of infections, but the risk of more severe invasive infections is unclear.

Using data from the HUNT2 study in Norway (1995 - 1997), investigators prospectively examined if three insomnia symptoms mirroring DSM-IV and two insomnia symptoms mirroring DSM-IV criteria were associated with the risk of clinically relevant BSI with verified microbes and risk of BSI-related mortality.

All individuals aged ≥20 years (n = 93,989) in the geographical study location were invited to participate and a total of 53,536 individuals were included in the analytical sample after exclusions. Investigators defined the outcome variable as first-time BSI and BSI-related mortality as BSI registered ≤30 days prior to death.

Participants were followed-up until they experienced an event or end of follow-up until December 2011. In the questionnaire, all (≥20 years) were asked about DIS and DMS, whereas NRS was only determined in participants aged 20 –69 years.

Cox regression allowed investigators to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for first-time BSI and for BSI-related mortality associated with insomnia symptoms.

Over the median study follow-up of 14.9 years, 1,579 (3.0%) of participants had an episode of BSI and 284 (0.5%) BSI-related mortality.

In comparison to those reporting “no symptoms of insomnia”, individuals experiencing DIS often/almost every night had a HR of 1.14 (95% CI, 0.96 - 1.34), while those reporting DMS had a HR of 1.19 (95% CI, 1.01 - 1.40) for BSI. Meanwhile, individuals experiencing NRS once a week or more had a HR of 1.23 (95% CI, 1.04 - 1.46).

Participants who experienced all cumulative symptoms reflected in the DSM-IV insomnia definition were associated with an HR of 1.39 (95% CI, 1.04 - 1.87). Those having both DIS and DMS were associated with an HR of 1.15 (95% CI, 0.93 - 1.41).

Investigators added that participants who responded positively to “being troubled by insomnia to such a degree that it affected work performance” had a HR of 1.41 (95% CI, 1.08 - 1.84) compared to those responding negatively.

“The HRs for BSI-related mortality suggest an increased risk with increasing insomnia symptoms, but the CIs are wide and inconclusive,” Thorkildsen added.

The study, “Insomnia symptoms and risk of bloodstream infections: prospective data from the prospective population-based Nord-Trøndelag Health Study (HUNT), Norway,” was published in the Journal of Sleep Research.