Major Depression is a risk factor for Shorter Time to First Cigarette Irrespective of the Number of Cigarettes Smoked Per Day: Evidence from a National Population Health Survey

Abstract

Nicotine Dependence (ND) as measured by reduction in the Time to First Cigarette (TTFC) after waking and the roles of the number of cigarettes smoked per day (CPD) and stress as explanatory variables of this association. Methods: 10-years of follow-up data from the National Population Health Survey (NPHS) were used. The analyses were based on this nationally representative sample of the Canadian population who were over the age of 12 years in 1996 (n=13,298). The NPHS included measures of MD and TTFC. Shorter TTFC was defined as TTFC within 5 minutes of waking. Heavy smoking (HS) was defined by smoking 20 or more CPD. Using proportional hazard (PH) models, unadjusted and adjusted hazard ratios (HRs) for shorter TTFC were estimated for those with and without MD. Results: The unadjusted HR for shorter TTFC among those with MD versus those without MD was 3.7 (95% CI: 2.6-5.3, p<0.001). MD predicted onset of shorter TTFC even after adjustment for HS and tendency to smoke more under stress (HR: 1.7; 95% CI: 1.1-2.5, p=0.02). When TTFC was defined using longer cut-offs (30 minutes and 60 minutes), HS completely accounted for the effect of MD on TTFC onset. Conclusions: MD appears to be a risk factor for transition to shorter TTFC independent of effects of HS and the tendency to smoke more under stress. As MD is often modifiable, the above association points towards a preventive opportunity in relation to worsening of ND.