Serum copper, zinc and high-sensitivity C-reactive protein in short and long sleep duration in ageing men

Serum levels of zinc and copper have been proposed to associate with sleep duration. Mechanisms, such as inflammatory processes, have been suggested to relate this association. However, earlier studies have been conducted in small sample sizes. Human studies investigating the suggested associations while controlling for potential confounding factors are lacking.

Population-based data consisted of 2570 men (aged 42-60 years) from Eastern Finland. The participants reported an estimate of their sleep duration. The serum levels of zinc (S-Zn), copper (S-Cu) and high-sensitivity C-reactive protein (hs-CRP) were measured. Analysis of covariance was used for multivariate analyses.

S-Zn levels and Zn/Cu ratio were lowest in ≤6h sleep. S-Cu levels were highest in ≥10h sleep. Elevated levels (>3.0mmol/l) of hs-CRP were observed in ≤6h and ≥10h sleep. After adjustments for age, cumulative smoking history (pack-years), alcohol consumption (g/week), Human Population Laboratory depression scale scores, physical activity (kcal/day), cardiometabolic syndrome, and cardiovascular disease history, sleep duration was significantly associated with levels of both S-Cu and hs-CRP. The association with S-Cu remained statistically significant following further adjustment for hs-CRP in the same model.

Our data suggests an association between S-Cu and sleep duration in ageing men. Elevated inflammation (measured as serum hs-CRP) does not explain this relationship. Mechanisms underlying the relationship require further investigation, as S-Cu may contribute to sleep regulation through pro-oxidative processes and copper-dependent N-methyl-d-aspartate receptor activity.