title: [Monthly distribution of insomnia patients' birth].
abstract: OBJECTIVE
  To investigate whether the monthly distribution of birth is associated with insomnia.
  
  
  METHODS
  The monthly distribution of birth of 1020 consequent patients with insomnia who visited the Third Hospital of Peking University, 439 males and 581 females, aged 54 (22 - 86), was investigated and compared with that of 13254 cases of healthy newborn children born in the same hospital 1994 - 2004.
  
  
  RESULTS
  114 of the 1020 patients with insomnia were been born in January (11.2%), 90 in February (8.85%), 65 in March (6.4%), 67 in April (6.6%), 56 in May (5.5%), 56 in June (5.5%), 66 in July (6.5%), 78 in August (7.6%), 64 in September (6.3%), 91 in October (8.9%), 126 in November (12.4%), and 147 in December (14.4%). The structural ratio of the number of insomnia patients was the highest for those who were born in the months November, December, and January, and was the lowest for those who were born in May, June, and July. The number of insomnia patients who were born in the wintery months, November, December, and January, was 387 (37.9%), much more than those who were born in the May, June, and July (178 cases, 17.4%). The structural ratios of the insomnia patients who were born in different months were not significantly different between the 2 sexes (chi(2) = 12.769, P > 0.05). There was no significant differences in the structural ratios of the number of healthy newborn children who were born in different months. However, the monthly distribution of birth of the patients was statistically significantly different between the patients with insomnia and the healthy newborn children (chi(2) = 75.098, P < 0.01).
  
  
  CONCLUSIONS
  Month of birth is associated with insomnia. Those born in November, December, and January are more susceptible to insomnia.
authors.affiliation: Department of Neurology, Third Hospital of Peking University, Beijing 100083, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.forename: Zhi-Jie
authors.initials: ZJ
authors.lastname: Yang
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Fan
authors.forename: Zi
authors.initials: Z
authors.lastname: Yang
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.forename: Xiao-Gang
authors.initials: XG
authors.lastname: Li
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wei
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001723:Birth Rate; D016009:Chi-Square Distribution; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D012621:Seasons; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology*; D013997:Time Factors