Therefore, the purpose of this study was to determine (a) whether early pubertal timing effects on age at smoking onset existed for both White and Black girls and (b) whether the association between pubertal timing and age at smoking onset was moderated by race. Methods Participants The participants were girls enrolled in a longitudinal study on smoking, MEK162 chemical structure mood, and its impact on bone and reproductive health in adolescent girls (N = 264). Participants were primarily White (62.1%) or Black (32.6%). The remaining 5.3% of the girls were biracial or other race/ethnicities and were combined with the Black group. Participants were recruited from an urban teen health center and the surrounding community. Data for the present study were from the first assessment, which took place from December 2003 to October 2007.

Girls were enrolled in the study by age cohorts (11, 13, 15, and 17 years) based on the cross-sequential design (Miyazaki & Raudenbush, 2000), and an eligibility questionnaire based on five previously defined levels of smoking experience ranging from ��not even a puff�� to daily smoking. Smoking categories were based on modifications to the methods of Mayhew, Flay, and Mott (2000) and consisted of (a) ��Never-smoker,�� defined as zero puffs of a cigarette across the lifetime; (b) one puff to two cigarettes in lifetime; (c) smoked 3�C99 cigarettes or more than 100 but none in the last 30 days; (d) smoked more than 100 cigarettes in lifetime and 1�C19 days of the last 30 days; and (e) smoked more than 100 cigarettes and 20�C30 days of the last 30 days.

Exclusion criteria were (a) pregnancy or breast feeding within the past 6 months, (b) primary amenorrhea (>16 years) or secondary amenorrhea (<6 cycles/year), (c) body mass index less than the first percentile or body weight greater than 300 pounds, (d) medication/medical disorder influencing bone health, and (e) psychological disabilities impairing comprehension or compliance. This study received approval from the hospital��s institutional review board. Procedures Participants came to an urban children��s hospital for study visits. After consent and assent were obtained, the parent was directed to a separate room to complete questionnaires. The adolescent then had a physical examination, during which time, a standardized interview was conducted focusing on menstrual history. Other procedures followed but were not the focus of this paper. The protocol also included Anacetrapib the Diagnostic Interview Schedule for Children, which assessed cigarette use. Measures Pubertal timing Age at menarche (in years and months) was obtained through a clinician interview with the adolescent.