Sleep and headache are linked in a bidirectional way. Breathing quality during sleep may be a possible link between them. The objective of this study were to evaluate the prevalence of headache--and of allodynia--in a population of subjects who underwent cardiopulmonary monitoring during sleep for presumed respiratory problems; to evaluate the possible relationships between the presence of headaches--and of allodynia--and respiratory parameters. We studied 181 subjects, 112 without headache (mean age 59.4 ± 13.1 years, 97 men and 15 women); 69 with history of headache (42 men and 27 women; 41 migraineurs and 28 with tension type headache). Headache diagnosis was made according to ICHD-II criteria. A semi-structured ad hoc questionnaire was used to evaluate the presence of allodynia. Full cardiopulmonary monitoring was performed by SOMNO check(®) effort (WEINMANN) with SaO(2), T90 and AHI determination. Headache and headache-associated allodynia were particularly frequent in this population, suggesting a positive correlation between breathing problems during sleep and head pain, and allodynia. The observation that better respiratory parameters were found among headache sufferers with respect to those without headache, even in allodynic subjects, seems to reverse this point of view: headache and allodynia may possibly have an allostatic function preventing deep sleep and, in turn, avoiding prolonged apneas.