title: The Relationship between Nicotine Dependence and Age among Current Smokers.
abstract: BACKGROUND
  A recent study indicates that the incidence of smoking cessation varies with age. Although nicotine dependence (ND) has been regarded as one of the most significant barriers of successful smoking cessation, few researches have focused on the relationship between nicotine dependence and age.
  
  
  METHODS
  A cross-sectional study (conducted in 2013) with 596 Chinese rural male current smokers was performed to study the relationship between ND and age. The ND level was assessed using the Fagerström Test for Nicotine Dependence (FTND) scale. The univariate two-degree fractional polynomials (FPs) regression was used to explore the relation of ND to age.
  
  
  RESULTS
  The mean of FTND scores in the middle-aged group (45-64 yr old) was higher than that in the younger (<45 yr old) and older groups (≥65 yr old). The FPs regression showed an inverse U-shaped relationship between ND and age.
  
  
  CONCLUSIONS
  The middle-aged current smokers had higher degree of ND than the younger and the older groups, which showed an inverse U-shaped relationship between ND and age. This finding needs to be confirmed by further researches.
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Huijie
authors.initials: H
authors.lastname: Li
authors.affiliation: Zibo Center for Disease Control and Prevention, Zibo, P.R. China.
authors.forename: Yunping
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Suyun
authors.initials: S
authors.lastname: Li
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Lulu
authors.initials: L
authors.lastname: Pan
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Yang
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Fan
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Mingkui
authors.initials: M
authors.lastname: Han
authors.affiliation: Dept. of Epidemiology and Biostatistics, Shandong University, Jinan, P.R. China.
authors.forename: Chongqi
authors.initials: C
authors.lastname: Jia
keywords: Age; China; Nicotine dependence; Smoking; Tobacco