Association of daily sleep duration with the incident dementia by serum soluble TREM2 in a community

Background: Little is known about the influence of serum level of soluble triggering receptor expressed on myeloid cells 2 (sTREM2), which is a soluble type of an innate immune receptor expressed on the microglia, on the association of the daily sleep duration with the risk of dementia. Methods: A total of 1230 Japanese community-residents aged 60 and older without dementia were followed prospectively for 10 years (2002–2012). Serum sTREM2 levels were divided into two groups using the median value (334.8 pg/ml). Self-reported daily sleep duration was grouped into three categories of <5.0, 5.0–7.9, and ≥8.0 h. A Cox proportional hazards model was used to estimate the hazard ratios (HRs) and their 95% confidence intervals (CIs) of daily sleep duration on the risk of dementia according to serum sTREM2 levels. Results: During the follow-up, 262 subjects developed dementia. In subjects with low serum sTREM2 levels, subjects with ≥8.0 h of daily sleep had a significantly greater risk of dementia (multivariable-adjusted HR 2.05 [95% CI 1.32–3.19]) than those with 5.0–7.9 h of daily sleep, but those with <5.0 h did not. In contrast, the risk of dementia increased significantly in subjects with both <5.0 (1.95 [1.03–3.68]) and ≥8.0 h of daily sleep (1.48 [1.06–2.07]) in the subjects with high serum sTREM2 levels. Conclusions: The influence of daily sleep duration on risk of dementia differed according to serum sTREM2 levels in the older Japanese population. Short daily sleep may be associated with greater risk of dementia only in subjects with a high serum sTREM2 level.