title: Circadian patterns of ad libitum smoking by menstrual phase.
abstract: OBJECTIVE
  Recent research suggests nicotine metabolism may be influenced by sex hormones. Thus, we hypothesized that circadian smoking patterns would vary by menstrual phase.
  
  
  METHODS
  Healthy female smokers (n = 31) between the ages of 18 and 40 with regular menstrual cycles, and not using hormones or psychotropic medications, were recruited for a randomized clinical study. Subjects recorded the time of each cigarette smoked and their menstrual phase with daily diaries prospectively for one complete menstrual cycle of ad libitum smoking. Analyses included Poisson regression to assess variations in the rate of smoking during waking hours (i.e., 6:00 a.m. and 12:00 midnight) and circadian smoking patterns by menstrual phase.
  
  
  RESULTS
  Participants were 29.61 +/- 5.44 years of age and smoked 16.93 +/- 5.37 cigarettes per day. Participants had a lower rate of smoking during waking hours in the follicular phase as compared to the menses phase. There were no significant menstrual phase differences in the circadian smoking patterns.
  
  
  CONCLUSIONS
  These results offer further support for the influence of sex hormones on smoking behavior, but not on circadian patterns of smoking. Additional research is needed to study the direct relationship between nicotine metabolism, sex hormones, menstrual phase, and smoking behavior.
authors.affiliation: University of Minnesota, Minneapolis, 55414, USA. alle0299@umn.edu
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Allen
authors.forename: Marc
authors.initials: M
authors.lastname: Mooney
authors.forename: Rima
authors.initials: R
authors.lastname: Chakraborty
authors.forename: Sharon S
authors.initials: SS
authors.lastname: Allen
mesh_terms: D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D005498:Follicular Phase / Q000502:physiology; D005500:Follow-Up Studies; D006801:Humans; D008597:Menstrual Cycle / Q000502:physiology*; D008598:Menstruation / Q000502:physiology; D016012:Poisson Distribution; D011446:Prospective Studies; D012907:Smoking; D055815:Young Adult