Researchers who have followed 5,840 people from before birth to the age of 31 have found evidence suggesting that small size at birth and excessive weight gain during adolescence and young adulthood may lead to low grade inflammation, which, in turn, is associated with an increased risk of developing heart disease.
Previous epidemiological studies have linked environmental factors in early life with the risk of disease in adulthood, and this study identifies a possible causal mechanism. The study, which is published in Europe's leading cardiology journal, the European Heart Journal today (Thursday 10 April), underlines the important role of healthy lifestyles, from the foetal period, through childhood, adolescence and young adulthood, in preventing heart problems.
The researchers used a protein called C-reactive protein (CRP) as a marker for general inflammation. CRP is secreted from the liver, is present in blood, and slightly elevated levels can indicate a chronic inflammatory state (low grade inflammation, as opposed to acute inflammation).
“Low grade inflammation is important because it has been associated with future cardiovascular events in many population studies over the past few years and it may play a role in the development of cardiovascular disease,” explained one of the authors, Paul Elliott, Professor of Epidemiology and Public Health Medicine and head of the Department of Epidemiology and Public Health at Imperial College London.
Prof Elliott and his colleagues found that when the Finnish participants in the study reached the age of 31, CRP levels were 16% higher per 1 kg lower birth weight, 21% higher per 10cms shorter length at birth, and 24% higher per 1 kg/m3 lower at birth (kg/m3 is known as ponderal index), after adjusting for potential confounding factors. People who were amongst the smallest at birth, but who then put on the most weight up to the age of 31, had the highest average CRP levels. Every extra kg/m2 (body mass index, BMI) gained from the age of 14 to 31 was associated with a 16% rise in CRP levels; this association was greatest for people who had the highest BMI at 14.
Dr Ioanna Tzoulaki, the first author of the study and Lecturer in Epidemiology at the Department of Epidemiology and Public Health, Imperial College London, said: “We compared birth weight of children participating in the Finland 1966 Birth Cohort study with their CRP levels at age 31, and we found that those who had lower birth weight, have higher CRP levels when they are adults, and also the other way round – people who had higher birth weight had lower CRP levels as adults. The ‘lower' and ‘higher' CRP levels are relative to measurements in other participants in the study.
“These findings lead us to conclude that small size at birth and excessive weight gain during adolescence and young adulthood may predispose to low grade inflammation, which, in turn, is associated with increased risk of developing cardiovascular disease.”