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A review of existing studies carried out by scientists at the University of Tampere has found that people of short stature may be at greater risk of coronary heart disease.
Fotini Rozakeas, cardiac nurse at the British Heart Foundation, said:
“This study provides an interesting insight into the potential link between height and heart disease, but there needs to be more time and money spent researching this peculiar association.
“It’s the first time this association has been looked at using the combination of results from several different studies and, despite a number of theories, it is still unclear why short people should have an increased risk of heart disease.
“Whilst height is used to calculate Body Mass Index – a marker that might help indicate a risk of heart disease – there are lots of other risk factors to take into account like high blood pressure, high cholesterol, smoking, diabetes and obesity.
“It doesn’t matter if you are tall, short or somewhere in between, it’s still so important to do regular exercise, eat a healthy and balanced diet, stop smoking and control your weight to protect your heart health.”
The following appraisal of the study was carried out by Bazian: Citation: Short stature is associated with coronary heart disease: a systematic review of the literature and a meta-analysis.” European Heart Journal. doi:10.1093/eurheartj/ehq155. Authors: Dr Tuula A. Paajanen and colleagues from the University of Tampere and Tampere University Hospital in Finland carried out this research. Funding: The study was funded by the Finnish Cultural Foundation, Tampere University Hospital, the Aarno Koskelo Foundation, and the Finnish Foundation for Cardiovascular Research. Study design: This was a systematic review and meta analysis of studies looking at whether short stature is associated with coronary heart disease. Study methods: The researchers searched established databases of the scientific literature to identify studies looking at the relationship between height and coronary heart disease. Their final search was carried out in December 2007. The results of included studies were then pooled to determine the effect of short stature on the risk of cardiovascular outcomes. The researchers only included English language systematic reviews, meta analyses, randomised controlled trials, clinical trials, cohort or case-control studies addressing their question. To be included, studies also had to: •,include over 200 participants; •,include healthy people or people with symptomatic coronary heart disease at the start of the study; •,look at the effect of height as a continuous variable or compare different height groups; •,look at important outcomes – including death from any cause, death from cardiovascular disease, death from coronary heart disease, or other cardiovascular outcomes; •,cohort studies had to follow up individuals for at least two years to assess these outcomes. The studies they identified compared differing height categories. The researchers decided to compare the shortest group in each study versus the tallest group, rather than specifying what heights would be considered “short” or “tall”. When pooling study results the researchers used accepted statistical methods to look at whether the studies had significantly different results, which would suggest that they should be pooled with caution. They used pooling methods that take into account differences between studies. Results of the study: The researchers’ initial searches identified 1,902 articles in their searches, and 52 of the studies described in these articles met the inclusion criteria. These studies included over three million people in total (3,012,747 individuals). Twenty two of these studies could be included in the statistical pooling of results, although not all of these studies contributed to all of the analyses. Across the studies, short individuals were on average less than 160.5cm tall (about five foot three inches) and the tall individuals over 173.9cm (about five foot eight inches) on average. The short individuals were about 35% more likely to die from any cause during follow up than the tall individuals (relative risk [RR] 1.35, 95% CI 1.25 to 1.44). They were also around 50% more likely to die from cardiovascular disease (CVD), or to have coronary heart disease (CHD, includes deaths from CHD), or to have a heart attack (RR for CVD death 1.55, 95% CI 1.37 to 1.74; RR for CHD 1.49, 95% CI 1.33 to 1.67; RR for heart attack 1.52, 95% CI 1.28 to 1.81). Overall, the shortest groups showed a 46% increase in the risk across all of the cardiovascular outcomes assessed compared with the tallest groups (54 results pooled from 22 studies; RR 1.46, 95% CI 1.37 to 1.55). Being short was associated with increased risk of these outcomes in both men and women. Researchers’ conclusions: The researchers concluded that there was a real association between short stature and risk of cardiovascular disease, with the shortest adults being at about 50% greater risk of coronary heart disease and related mortality than tallest adults. Strengths and limitations: The study’s strengths include: •,use of a good study design for summarising the available high quality research evidence on a question •,the fact that it systematically searched for and assessed studies, and used set inclusion/exclusion criteria to decide whether studies were eligible •,the large number of studies and individuals involved The study’s limitations include: •,The researchers pooled the relative risks across a range of different cardiovascular outcomes and gave a summary RR of 1.46 for the combined outcome. This also involved pooling multiple different outcomes from individual studies. It is not clear how appropriate this approach is, as although this tells us that overall risks of the outcomes assessed appear to be increased, it cannot tell us which outcomes are increased and may overestimate the link. •,Individuals who are shorter may differ from taller individuals in a number of ways, for example, in their socioeconomic status, nutrition, general health, and ethnicity. These other factors may themselves be contributing to the difference in cardiovascular risk seen between the shorter and taller groups (called confounding). It was not clear whether all studies took into account potential confounding factors, such as known cardiovascular risk factors. This means that it is hard to judge how much of the link seen may be due to these confounding factors. •,The researchers found that the studies pooled had differing results, which suggests that the pooled results should be interpreted cautiously. Although they did use appropriate analysis methods for this situation, ideally the researchers would have investigated why the study results differed (for example, were the differences due to differing study designs, populations, or outcomes assessed). •,The exact number of individuals included in each meta analysis was not reported, nor were absolute risks of the events in the individual studies. Overall this new study has looked at a large amount of data and although the reasons behind the link seen are not clear, the study does support the idea that there is a link. It is not possible to say how strong the link would be if all known cardiovascular factors were taken into account. Importantly, tall people are not completely protected from heart disease and therefore everyone is advised to pay attention to the major modifiable risk factors for heart disease: stopping smoking, improving diet and increasing physical activity.