Takeaway
Psychophysiological insomnia (PI) was associated with increased subsequent respiratory tract infections (RTIs) in adults, risk was increased in those who were also obese, and there was a correlation between neutrophil: lymphocyte ratio (NLR) and PI but only in men.
Why this matters
Adequate sleep has been considered an important factor for a functional immune system - this is supported by this study although the mechanism remains unclear.