Changes over time in the relationship between reactions to health warning labels and plans to quit smoking.

INTRODUCTION: The impact of health warning labels (HWL) on cigarette packaging appears to diminish over time. This study assesses the relationship between HWL reactions and changes in plans to quit smoking over time. METHODS: We analyzed data from the International Tobacco Control (ITC) Four Country Survey, focusing on daily smokers in Australia, England, and the US. We used self-reported measures of noticing HWLs (Noticing), HWL-triggered quit thoughts (Think Quit), and plans to quit smoking (Quit Plan) to compare data from peak HWL-response periods with more recent survey waves. Logistic regression models estimated the relationship between HWL reactions and Quit Plans, adjusting for demographics and smoking behavior. RESULTS: Australia and England showed declines in HWL reactions (Noticing and Think Quit) over time, while the US showed minimal decline in Noticing but notable decline in Think Quit and Quit Plans. Think Quit measure consistently predicted Quit Plans across all countries and time points, though strength of association varied (OR for "Think quit a lot" ranged from 4.92 to 6.15, all p < 0.001). Despite declining HWL reactions, Quit Plans remained stable in Australia and England, and suggest other influences (such as policy, pricing, or unmeasured sustained HWL effects) may support Quit Plans. CONCLUSIONS: Strengthened (i.e., more prominent) HWLs lose potency in triggering immediate reactions but likely retain a sustained role in reinforcing health concerns and maintaining quit motivation. Their long-term impact may be underestimated by short-term measures. Future research should develop tools that better capture cumulative HWL effects and distinguish them from other influences on cessation.