Life-course body mass index trajectories and blood pressure in mid life in two British birth cohorts： stronger associations in the later-born generation

Leah Li，Rebecca Hardy，Diana Kuh，Chris Power

1. Centre for Paediatric Epidemiology & Biostatistics，

2. MRC Unit for Lifelong Health and Ageing，University College London，UK

专家推荐

Life-course body mass index trajectories and blood pressure in mid life in two British birth cohorts： stronger associations in the later-born generation

Leah Li1*，Rebecca Hardy2，Diana Kuh2，Chris Power1

1. Centre for Paediatric Epidemiology & Biostatistics，

2. MRC Unit for Lifelong Health and Ageing，University College London，UK

学科：流行病与卫生统计学

推荐专家：邹延峰副教授（安徽医科大学公共卫生学院）

推荐论文：Leah Li，Rebecca Hardy，Diana Kuh，et al. Life-course body mass index trajectories and blood pressure in mid life in two British birth cohorts： stronger associations in the later-born generation ［J］. International Journal of Epidemiology，Accepted 20 May 2015，

10.1093/ije/dyv106

·专家点评·

近年来肥胖和体质指数（BMI）快速增加，它们对心血管疾病有何影响知之甚少。该研究在出生队列中调查了生命过程中的BMI轨迹与成年人的血压（BP）之间的关系。作者使用了1946年（样本量4787）和1958年（样本量16820）的两个英国出生队列。调查结果发现BMI轨迹和BP之间存在关联，在后出生队列中关联更强；BMI轨迹和BP之间的关联可能被其他因素影响，如饮食和吸烟。该研究结果为研究BMI轨迹和BP之间关联及高血压危险因素随着时间推移的改变情况提供了重要的理论依据和指导意义。

优点：1）前瞻性的大样本研究；2）使用了两个出生队列；3）使用了Joint multivariate response models；4）数据分析详实，合适的分层分析，结果展示清楚；

缺点：混杂因素对结果的影响还需进一步控制，如对高血压的治疗情况可能对结果产生一定的影响。

总的来讲，高血压的危险因素可能随着时间的推移而改变的情况应该需要更多的研究来探讨，在后出生队列中BMI轨迹和BP之间关联更强的可能原因也应该进一步探讨，混杂因素应该控制的更严。

Background： Little is known about the impact of recent increases in obesity and more rapid gains in body mass index（BMI）on cardiovascular risk factors. We investigated life-course BMI trajectories associations with adult blood pressure（BP）across two generations.

Methods： We used the the 1946 and 1958 British birth cohorts. Joint multivariate response models were fitted to longitudinal BMI measures ［7，11，16，20，26，36，43 and 50 y（years）： 1946 cohort，n=4787； 7，11，16，23，33 and 45 y： 1958 cohort，n=16820］ and midadult BP. We adopted linear spline models with random coefficients to characterize childhood and adult BMI slopes.

Results： Mean systolic BP（SBP）decreased from the earlier- to later-born cohort by 2.8 mmHg in females，not males； mean diastolic BP（DBP）decreased by 3.2-3.3 mmHg（both sexes）. Adult BMI was higher in the later- than the earlier-born cohort by 1.3-1.8 kg/m2，slopes of BMI trajectory were steeper from early adulthood and associations with adult BP were stronger. Associations between adult BMI and SBP were stronger in the later-born cohort. For males，childhood BMI slope was associated with SBP only in the later-born cohort； the association for adult BMI slope was stronger in the later-born cohort： correlation coefficient r=0.28 ［95% confidence interval（CI）： 0.25，0.33］ versus 0.13（0.06，0.20）. For females，childhood slope was associated with SBP in both cohorts； adult slope was associated with SBP only in the 1958 cohort ［r=0.34（0.31，0.37）］. Patterns of child-to-adult BMI associations were similar in relation to DBP.

Conclusions： BP did not increase between two generations born 12 y apart despite higher BMI levels. A stronger association between BMI trajectory and BP in the laterborn cohort suggests that BMI-related effects may have been offset by improvements in other factors linked to BP，such as diet and smoking.

Cohort study； blood pressure； BMI trajectories； joint modeling； life course

Key Messages

· Mean values of systolic or diastolic blood pressure（BP）did not increase between two generations born 12 years apart，despite the steeper slope for BMI changes from early adulthood and higher levels of body mass index（BMI）in mid adulthood in the later- than the earlier-born cohort.

· A stronger association between life-course BMI trajectories and higher BP levels in the later-born cohort suggests that BMI-related effects may have been offset by improvements in other factors linked to BP over successive generations in the UK.

责任编辑：王帅帅

* Corresponding author. Centre for Paediatric Epidemiology and Biostatistics，UCL Institute of Child Health，30 Guilford Street，London WC1N 1EH，UK. E-mail： leah.li@ucl.ac.uk.