Impact of Age at Smoking Initiation on Smoking-Related Morbidity and All-Cause Mortality

Abstract

Introduction: Using a nationally representative sample of U.S. adults, the aims of this study were to examine the impact of early smoking initiation on the development of self-reported smoking-related morbidity and all-cause mortality.

Methods: National Health Interview Survey data from 1997 through 2005 were linked to the National Death Index with follow-up to December 31, 2011. Two primary dependent variables were smoking-related morbidity and all-cause mortality; the primary independent variable was age of smoking initiation. The analyses included U.S. population of current and former smokers aged ≥30 years (N=90,278; population estimate, 73.4 million). The analysis relied on fitting logistic regression and Cox proportional hazards models.

Results: Among the U.S. population of smokers, 7.3% started smoking before age 13 years, 11.0% at ages 13-14 years, 24.2% at ages 15-16 years, 24.5% at ages 17-18 years, 14.5% at ages 19-20 years, and 18.5% at ages ≥21 years. Early smoking initiation before age 13 years was associated with increased risks for cardiovascular/metabolic (OR=1.67) and pulmonary (OR=1.79) diseases as well as smoking-related cancers (OR=2.1) among current smokers; the risks among former smokers were cardiovascular/metabolic (OR=1.38); pulmonary (OR=1.89); and cancers (OR=1.44). Elevated mortality was also related to early smoking initiation among both current (hazard ratio, 1.18) and former smokers (hazard ratio, 1.19).

Conclusions: Early smoking initiation increases risks of experiencing smoking-related morbidities and all-cause mortality. These risks are independent of demographic characteristics, SES, health behaviors, and subsequent smoking intensity. Comprehensive tobacco control programs should be implemented to prevent smoking initiation and promote cessation among youth.