Parents: does size matter?
By Linsay Gray
What can the height of a person tell us about them and their children? Although determined to an extent by genes, the height of a fully grown man or woman can be considered as a ‘marker’ of the circumstances they experienced early in life. These childhood circumstances include illness, living conditions, diet, and maybe even stress. Such early life circumstances have been shown to be linked to health risks later in life. In fact, the height of an individual is also linked with their chance of developing chronic health conditions. Taller people are at lower risk of heart disease, for example.
But what about the height of their parents? One may wonder if that could that have an effect? Evidence from studies of animals indicates that poor health which is caused by challenging circumstances during development early in life may be transmitted from generation to generation. The idea that compromised development in early life leads to negative effects on heart disease risk across generations in humans as well as animals has some support. In previous studies, taller parents tended to have children with favourable health profiles in terms of, for instance, lower blood pressure and less body fat. Also, deprivation – which is linked to small stature – appears to influence risk of heart disease across generations. The effect of the height of parents on risk of heart disease in their adult children has not previously been directly investigated in detail until now. It turns out a mother’s height may affect her child’s risk of developing heart disease in adulthood.
In a recent study, we combined data on 1,456 married couples in two Scottish towns who had their height measured during the 1970s with data on 2,306 of their adult children (the ‘offspring’) who had their health risk assessed in 1996 when aged 30-59 years. The offspring were followed to see if they were admitted to hospital or died from heart disease. This particular family-focussed study is unusual in that the second generation is middle-aged, whereas other similar studies tend to have younger offspring. The advantage of this is that the heights of the offspring reflect accurately the full adult heights achieved and have not yet been greatly affected by declines in height which generally occur at older ages.
We found that taller height in both parents was linked with a lower risk of heart disease in their offspring, but the association was stronger for the height of the mothers. The decrease in risk was 15% for every 5.6 cm increase in height of the mother. The association remained after we accounted for differences in age, sex, the height of the other parent, and factors in the offspring linked with heart disease risk, including their own height.
The stronger link with the height of the mother could be explained by stronger associations between health-related behaviours of mothers and their children, or the mother’s womb being affected by her own early life circumstances. In today’s world, the possibility of transmission of damaging effects of undesirable conditions during pregnancy from one generation to the next is particularly pertinent to populations of emerging economies. Countries such as China, India and Brazil are moving from traditional lifestyles –with often limited nutrition — to Western-style abundance. Current generations in these parts of the world typically have low birth weight on the one hand but subsequent build up of high body fat on the other hand — a combination known from other studies to be a health hazard. Indeed, these nations are presently experiencing rising levels of heart disease. Moves to improve nutrition in women of child-bearing age alongside measures to reverse the obesity epidemic could be useful in the global containment of heart disease in current and future generations. Yet to be explored are the associations of parent height with alternative causes of death such as cancers. In conclusion, our results indicate there is evidence of an association between taller parent height — particularly that of the mother — and lower risk of adulthood heart disease in their children. So, it seems the height of a person can tell us more than we may have expected.
Dr Linsay Gray is Senior Investigator Scientist at the MRC/CSO Social and Public Health Sciences Unit. She is on the editorial board of the Archives of Diseases in Childhood journal and is a Fellow of the Royal Statistical Society, leading in research collaborations with groups in Europe and the US. Dr Gray is co-author of the paper Parental height in relation to offspring coronary heart disease: examining transgenerational influences on health using the west of Scotland Midspan Family Study. Her co-authors were George Davey Smith, Alex McConnachie, Graham CM Watt, Carole L Hart, Mark N Upton, Peter W Macfarlane, and G David Batty. The paper has been made free for a limited time by the International Journal of Epidemiology.
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Image credit: Father measures height of child. Photo by SquaredPixels, iStockPhoto.