Trajectories of body mass index and overweight in early adulthood and blood pressure at 53 years
Background
Body mass index (BMI) is positively associated with blood pressure (BP) throughout adulthood. However, it is not known whether being overweight (BMI>25 kg.m2) earlier in adult life is associated with higher BP independent of current BMI, or whether there are sensitive periods for weight gain in adulthood.
Objectives
To explore the pathways by which being overweight in adulthood is associated with BP at 53 years.
Design
Prospective birth cohort study with information on BMI at 20, 26, 36, 43 and 53 years and BP at 53 years.
Outcome
BP at age 53 years. Censored regression models, accounting for individuals on antihypertensive medication, were used. To investigate a cumulative influence, we estimated the effect of time from being first overweight. To investigate sensitive period(s), we used standardised conditional BMI velocities for each interval. Lastly, an overweight trajectory was defined for each individual based on their status at 26, 36 and 53 years to try to formally assess the evidence for an accumulation or sensitive period pathway.
Results
Overweight at all ages was associated with a higher mean BP at 53 years. After adjusting for current BMI, only overweight at age 43 in men contained any additional information on BP at 53 years. Men who became overweight at 26 had a SBP 8.7 mm Hg higher (95% CI 4.4 to 13.0) than those first overweight at 53. Similar patterns but smaller associations were seen in women (p(interaction)<0.001). All periods of adult weight gain (26–36, 36–43, 43–53 years) were associated with a higher BP. The association varied little between periods, in males it ranged from a 2.7–3.6 mm Hg increase in SBP per SD increase in BMI velocity. BMI tracked strongly through adulthood, the BMI at 53 years in men first overweight at 26 was 30.9 kg.m2 (95% CI 30.5 to 31.4) compared to 26.4 kg.m2 (95% CI 26.3 to 26.6) in those first overweight at 53. Few individuals moved to a normal weight once overweight, this prevented a reliable estimation of the excess risk associated with prolonged overweight and meant it was difficult to disentangle a sensitive period or accumulation pathway using the different trajectories of overweight.
Conclusion
Early adult overweight and all periods of adult weight gain irrespective of earlier BMI were associated with a higher later life BP. Associations at younger ages appear to be largely mediated through BMI tracking. This highlights the importance for later health of preventing overweight in early adulthood.
