Exploring brief measures of nicotine dependence for epidemiological surveys

Abstract

A score≥6 in the Fagerström Test for Nicotine Dependence (FTND), identifying high nicotine dependence, was compared with three briefer classifications: (1) Item 4: heavy smoking (more than 30 cigarettes per day); (2) Item 1: high early smoking (smoking within 30 min of waking up); and (3) a score≥4 by combining Items 1 and 4. The FTND scores from 1642 smokers from five samples in the US and Spain were analyzed. Heavy smoking had low sensitivity. High early smoking had low specificity. A score≥4 by combining Items 1 and 4 had relatively good sensitivity (94%) and specificity (88%). Researchers needing definition of nicotine dependence briefer than FTND may want to only use Items 1 and 4 of FTND with a cutting score≥4.

Introduction

The Fagerström Test for Nicotine Dependence (FTND) is the most widely used instrument to establish and quantify nicotine dependence (Heatherton, Kozlowski, Frecker, & Fagerström, 1991). The importance of FTND is that it may help to predict the success at stopping smoking. The FTND has six items that provide a total score ranging between 0 and 10. Two items of the FTND, Item 4 (the number of cigarettes per day; scored between 0 and 3), and Item 1 (the time to the first cigarette of the day; scored between 0 and 3), may be the most important items to reflect dependence (Kozlowski, Porter, Orleans, Pope, & Heatherton, 1994). The combination of these two items has been called the Heavy Smoking Index (HSI) since Heatherton, Kozlowski, Frecker, Rickert, and Robinson (1989) demonstrated its validity in three samples of smokers studied by using biological measures of smoking. In spite of some psychometric problems Haddock et al., 1999, Kozlowski et al., 1994, Payne et al., 1994, Pomerleau et al., 1994, the FTND continues to be the most widely used instrument to measure nicotine dependence all over the world. Fagerström et al. (1996) proposed that a FTND score of 6 or higher identifies subjects with high nicotine dependence.

In the past, epidemiological surveys have focused on the prevalence of tobacco smoking. A more recent survey focused on nicotine dependence points out that there is a need for changing the focus of epidemiological surveys of the general population from tobacco smoking to nicotine dependence (Breslau, Johnson, Hiripi, & Kessler, 2001). In the past, attempts to establish measures of nicotine dependence have been limited to prevalences of heavy smoking, which is usually defined as consuming more than 20 to more than 30 cigarettes per day. Heavy smoking is considered a gross indicator of high nicotine dependence.

Certainly, new epidemiological surveys may require brief measures of nicotine dependence. Ideally, the FTND can be used in some surveys but six questions may be too lengthy for many other surveys including hundreds of other questions. This study explores the use of FTND Items 1 or 4 or the combination of both items as brief measures of high nicotine dependence. The cut-off point of 6 in the FTND for classifying individuals as those with and without high nicotine dependence is considered as the “gold standard.” This gold standard is compared with: (1) a dichotomous classification of Item 4 that is equivalent to heavy smoking (smoking more than 30 cigarettes or having a score of 3 in Item 4); (2) a dichotomous classification of Item 1 (having a score of 2 or higher or smoking within 30 min) that has been used in one epidemiological survey (Son, Markovitz, Winders, & Smith, 1997) but has never been studied; and (3) a dichotomous classification of the HSI or what is the same the combination of Items 1 and 4 (having a score of 4 or higher).

Several samples described before Aguilar et al., submitted for publication, Becoña & Vázquez, 1998, de Leon et al., in press, Gonzalez-Pinto et al., 1998, Jurado et al., submitted for publication are used to conduct these new analyses. The objective of this study is to analyze the kappas, percentage of disagreement, and sensibility/specificity of three brief definitions of high nicotine dependence by comparing with the gold standard, a score≥6 in the FTND. The three brief definitions of nicotine dependence are heavy smoking (score=3 in Item 4); high score in early smoking (score≥2 Item 1) and a high HSI score (score≥4 in the addition of Items 1 and 4).