Fig 1. Association between cigarette smoking (per 5 pack-years) and percent differences (95% CI) in mitochondrial DNA copy number (log-transformed N/S ratio), stratified by sex and race/ethnicity.

* Estimates were calculated based on model adjusted for age (years), sex, race, education (post-college vs college or under), income (<$50,000 vs ≥ $50,000), body mass index categories (18.5–24.9, 25.0–29.9, ≥ 30 kg/m²), total physical activity (<5, 5–29.99, ≥ 30 MET-hours/week), alcohol consumption (daily vs less than frequent daily), smoking use (<30 or ≥ 30 smoking pack-years) and depression category (past but not current history of depression or prevalent depression vs no prior history of depression), multivitamin use, comorbid conditions (hypertension, diabetes and use of cholesterol lowering medication).