STATS ARTICLES 2010
Are short people at greater risk of heart attack than tall people?
Rebecca Goldin Ph.D and & Jing Peng, June 28, 2010
A slew of studies about risks to your heart hit the news over the past couple of weeks: You’re at higher risk of cardiovascular disease if you are short, if you live in a polluted area or if you eat a diet low on the Mediterranean scale, and folic acid is not going to help a whit (but when there was good news, such as evidence that heart attacks are on the decline in California, the national media were not interested). Did the media capture what these studies really said? Over the course of this week we’ll be looking at each of these studies in depth and how the media covered the findings.
Short Stature and Cardiovascular Diseases (CVD)
The authors of the study published in the June issue of the European Heart Journal collected almost 2,000 articles on whether short stature and cardiovascular disease were linked. These dated from the early 20th century to more recent studies, and encompassed many differentdemographic groups and methods of analysis. For the purposes of simplification, the authors compared the tallest people to the shortest ones.
The inverse relationship between short stature and CVD is consistent among the studies, even under rigorous standards for inclusion in this analysis. Among the 1,907 articles identified on the topic, researchers selected only 52 studies that were sufficiently rigorous for review and meta-analysis. These comprised population-based follow-up studies, patient cohorts followed after a coronary heart event, and case-control studies, totaling 3,012,747 individuals.
The study attempted to compare the shortest people with the tallest using data from a variety of countries in which height varied significantly. On average, the shortest men were below 165.4cm (5 ft 4.3 in) and the shortest women were below 153.0cm (5 ft). Tall men were on average above 177.5cm (5ft 8in) in height, and tall women were over 166.4 cm (5ft 4.6in) in height. Short people had approximately a 50 percent higher risk of having a heart attack or dying from a heart attack compared to tall people.
Of the 52 studies, 22 provided adequate data for a meta-analysis based on risk ratios (RRs). From a total of 30 studies, it was not possible to extract RRs. They also used odds ratios (ORs), hazard ratios (HRs), and other variables separately when it was impossible to calculate RRs.
Meta-analysis shows that risks for different kinds of cardiovascular events are higher within the group of short people, compared with the number of event in the people in the tallest height categories. The combined RR was 1.46 (95% CI 1.37-1.55), suggesting that the result is statistically significant. The combined RR for all-cause mortality for short men was 1.37 (1.29-1.46) and women was 1.55 (1.41-1.70), meaning that the association between short stature and cardiovascular diseases is stronger for women than for men.
The study was unable to answer the question of what the "cutoff" is for the best height in relation to cardiovascular disease. As a general rule, the weakness in meta analyses is that they may reflect publication bias or systematic bias in the studies they re-evaluate. In this case, the original studies often did not have the height/CVD relationship as an end point, which lends it a little more resistance to publication bias.
The results were robust, though weaker in the United States than in other countries. For example, in the Physicians Health Study, there was a significant association between height and heart attack, but not between height and death due to heart attack. Similarly, in the Framingham Heart Study, there was no association between height and death due to heart attack, though short women had an elevated risk of heart attack.
News coverage: the contrast between what was reported in the press and in the scientific article
MSNBC, for example, neglected to distinguish between men and women, reporting their heights as an average among all people. This is a significant error because short women are at increased risk than short men. Many news accounts pointed to the importance of diet and smoking as having more influence than height. Certainly, these behaviors are in our control, while our height is not; however, by emphasizing factors within our control and not our stature, journalists missed one of the most important conclusions of the article, namely:
“Height is used to calculate body mass index (BMI), which is a widely used quantity risk of CHD. The value of BMI has been recently questioned by reports showing that BMI may not associate with the severity of CHD in angina patients with chronic kidney disease or may even be inversely associated. This has been discussed as the obesity paradox. The results of this meta-analysis suggest that height may be considered as a possible independent factor to be used in CHD risk calculations.”
In other words, shortness should be taken into consideration even if it is not in our control.
The review also pointed to the possibility of short stature is associated with the risk of CHD and MI through the effect of smaller coronary artery diameter. The theory is that the smaller coronary arteries of short people may be occluded earlier in life compared to those of tall people under similar risk conditions. This could have important impact on treatment for possible heart disease.
Moreover, recent findings on the genetic background of body height suggest that inherited factors rather than speculative early-life poor nutrition or birth weight may explain the association between small stature and later-life increased risk for CHD events. In contrast to the study, MSNBC declared that scientists aren’t sure why short people might be more susceptible to heart problems, but think there could be several explanations.
Taken as a whole, the relationship between short stature and CVD seems to be real. The systematic review and meta-analysis show that adult short stature poses about 1.5 times higher risk for CHD morbidity and mortality than being a tall individual. Many media accounts underestimated the effect of short stature on cardiovascular disease. Although the effect of lifestyle habits such as smoking, drinking, exercise and diet should not be neglected, the message from this study is that people should not only focus on the heart risk factors they can control; short people should be encouraged to be extra vigilant when it comes to heart disease.