C4A and infection: Forty-two patients with chronic insomnia (age = 64.44 ± 10.53) and 47 normal controls (age = 67.08 ± 7.822) were selected to determine differences in data, such as complete blood counts (CBCs), biochemical indices, lymphocyte subsets, immunoglobulin (Ig), complement C3 and C4 and interleukin-6 (IL-6), as well as to compare the incidence of clinical infection between the two groups.