Abstract
INTRODUCTION: Nicotine dependence measures often rely on self-reported cigarette consumption, which has declined over time and may not accurately reflect nicotine intake. We developed a brief two-item Short Nicotine Dependence Index (SNDI) assessing urge to use and difficulty abstaining, and examined its association relative to that of the established Heaviness of Smoking Index (HSI) with saliva cotinine, a biomarker of nicotine exposure. METHODS: Data were drawn from the Health Survey for England (HSE; 2000-2021) and a London General Practice Survey (GP Survey; 1989) (n = 14 244 current cigarette smokers aged ≥16 with valid cotinine data). Dependence was assessed using two questions: time to first cigarette after waking (scored 1-6) and perceived difficulty going a whole day without smoking (scored 0-3). Scores were summed to produce a total SNDI score (range 1-9). Mean cotinine levels were estimated across item responses and total scores in each sample. RESULTS: Cotinine concentrations increased consistently with higher scores on both individual items and the total SNDI score. In the HSE, cotinine ranged from 83 [95% CI = 77% to 88%] ng/mL for those with the lowest total score to 387 [377-396] ng/mL for those with the maximum score. A similar gradient was observed in the GP Survey (from 92 [75-110] to 431 [399-463]), despite higher overall cigarette consumption. In both datasets, the SNDI explained more variance in cotinine than the HSI: R2 = 0.304 vs. 0.278; GP Survey: 0.283 vs. 0.250. CONCLUSIONS: The SNDI is a brief self-report measure that outperforms existing short tools in predicting nicotine exposure. It offers a practical alternative for research and community surveillance in evolving nicotine use landscapes. IMPLICATIONS: The Short Nicotine Dependence Index offers an efficient and practical alternative to traditional dependence measures that rely on cigarette consumption. Its brevity and strong correlation with biochemical markers make it well-suited for use in large-scale surveys and clinical settings. By focusing on observed behavior (time to first cigarette) and self-reported difficulty abstaining, it remains relevant as smoking and nicotine use patterns shift. In addition, because it does not use reported cigarettes smoked per day, it may be useful for assessing dependence on other nicotine products (eg, e-cigarettes). Further research is needed to evaluate its validity among users of other nicotine products.