[Distribution characteristics of smoking behavior among adult twins in China]

This study aims to describe the population and regional distribution characteristics of smoking behavior among adult twins in the China Twin Registry (CNTR), as well as the concordance rates for smoking behavior in monozygotic and dizygotic twins, and estimate the heritability. The study population included adult twins in CNTR who had smoking questionnaire data. A random-effects regression model was used to describe the distribution of smoking behavior among different subgroups based on various characteristics. The concordance of smoking behavior between different zygosity groups was calculated, and heritability was estimated. A total of 28 444 twin pairs were included in this study, with an average age of (36.6±12.0) years. Among male twins, 41.2% were current smokers, while only 1.2% of females smoked. Higher smoking rates were observed among male smokers in the 50-59 age group (z=23.0, P<0.001), northern regions (z=2.9, P<0.01), rural areas (z=-5.2, P<0.001), those who were divorced/widowed (z=3.8, P<0.001), and first-born twins (z=-4.3, P<0.001), while lower smoking rates were found in those with higher education (z=-16.1, P<0.001) and unmarried individuals (z=-16.0, P<0.001). The smoking concordance rate for male monozygotic twins was 69.6%, significantly higher than the 57.3% concordance rate for dizygotic twins (χ²=105.0, P<0.05). The heritability of smoking behavior in male twins was estimated at 28.9% (95%CI: 24.3%-33.4%). Stratified analyses showed differences in heritability across regions and age groups: the heritability in northern regions was 32.6% (95%CI: 27.3%-38.0%), higher than the 21.0% (95%CI: 12.4%-29.5%) observed in southern regions; the highest heritability of 35.1% (95%CI: 26.3%-43.9%) was found in the 18-29 age group, with heritability decreasing with age. In conclusion, the smoking rate and influencing factors in the twin population are similar to those in the general population, with unique characteristics, such as higher smoking rates in first-born twins. Genetic factors have a significant impact on smoking behavior.