Exposure to maternal smoking during pregnancy and lifelong smoking: Association with vertebral dimensions in middle age

Exposure to maternal smoking during pregnancy is negatively associated with bone development, however, some studies have reported null findings. Offsprings' smoking behavior may also relate to bone structure. However, it is unclear whether smoking relates to vertebral size. We investigated whether maternal smoking during pregnancy or offsprings' lifelong smoking from ages five years to 46 years is associated with vertebral dimensions in middle age. A total of 566 offspring from the Northern Finland Birth Cohort 1966 underwent lumbar magnetic resonance imaging at age 46 years. Complete data were available. We utilized previously identified maternal smoking trajectories and offsprings' lifelong smoking trajectories as exposures, used cross-sectional area (CSA) and volume of the fourth lumbar vertebra as study outcomes, and considered sex, parental socioeconomic status, lifelong body mass index, lifelong physical activity, and education as potential confounders in general linear models. The "late adult quitters" were associated with larger CSA (Beta [B] coefficient 0.9, 95 % confidence interval 0.4-1.5) and volume (2.2, 0.4-4.0) than the "non-smokers." After adjustments, the B coefficient of CSA attenuated but remained statistically significant (0.5, 0.1-0.9), while the B coefficient of the volume attenuated to non-significant (0.7, -0.6 to 2.0). Other lifelong smoking trajectories or maternal smoking trajectories during pregnancy were unrelated to the study's outcomes. There was no negative association between vertebral size and lifelong smoking or maternal smoking during pregnancy. However, more research with larger samples and objective exposure data is warranted to confirm these findings.