Short natural sleep is associated with higher T cell and lower NK cell activities.

Short sleep duration increases the risk of several diseases, possibly involving compromised immune function. However, most previous studies are based on experimentally induced sleep deprivation, and only a few have studied natural variations in sleep duration. Thus our aim was to study how natural variations in sleep duration affect immune function. In total, 36 healthy men and women, aged 20-54, donated blood; 29 on three consecutive mornings, and seven on one morning. Each morning, participants self-reported sleep duration the night prior to blood draw. General sleep patterns, physical activity and stress were also assessed. A flow-cytometric assay was used to measure natural killer cell activity (NKCA), T cell function (in response to PHA, influenza, and SEA+B), and B cell function (in response to PWM) per volume whole blood. Short sleep duration prior to blood draw (<7 h) was associated with 49% higher PHA-induced T cell function (95% CI 7/109%) and 30% lower NKCA compared with normal prior sleep (7-9 h) (95% CI -46/-8%). In addition, high perceived stress was associated with 39% higher PHA-induced T cell function (95% CI 0/94%). High general physical activity was associated with 47% increased numbers of B cells and 28% increased numbers of T cells, but not with immune function. Our results suggest strong relationships between short sleep duration and T- and NK-cell functions. The stability of the findings as well as the clinical consequences of the link between short sleep and immune function should be explored in future studies.