A new study from Germany suggests that belly size and other markers of abdominal fat may be a better predictor of stroke than body mass index (BMI).
The study was the work of lead author Dr Yaroslav Winter from the University of Heidelberg and other colleagues based there and at other research and clinical centres in Germany, and is published online before print on August 14th in the journal Stroke.
Previous studies have already suggested that waist circumference is a better predictor of cardiovascular risk than body mass index (BMI), and Winter and colleagues wanted to see if this was the case for cerebrovascular events such as stroke and transient ischemic attack (TIA). TIA is commonly called mini stroke, where there is a temporary interruption to the blood supply to a part of the brain, and is often a precursor to a stroke, which is a permanent disruption to blood supply in a part of the brain.
For the case control study, Winter and colleagues enrolled 379 adults with stroke and/or TIA and matched them with 758 controls of the same age and sex living in the same region. 79 per cent (301 members) of the stroke/TIA group had had a stroke, 10 per cent (37) had had bleeding in the brain, and 11 per cent had had a TIA. The stroke/TIA group had an average age of 67 and comprised 141 women and 238 men.
The researchers took various measures of obesity, including BMI, waist to hip ratio, waist circumference and waist to height ratio (these last three being what they called markers of abdominal adiposity, or abdominal fat).
They then analysed the links between these measures and stroke or TIA risk using statistical tests like conditional logistic regression and adjusted for other risk factors.
The results showed that:
While there was a positive strong link between BMI and cerebrovascular risk, it became non-significant when the researchers took out risk factors like physical inactivity, smoking, blood pressure, and diabetes.
Markers of abdominal adiposity were strongly linked to risk of stroke/TIA, regardless of the other risk factors.
For instance, participants with bigger waists (more than 40 inches for men and 35 inches for women) had 4 times the risk of developing a stroke or TIA compared to those with more typical waist sizes.
Also, participants with the largest waist-to-hip ratio had nearly 8 times the risk of developing a stroke or TIA.
Winter and colleagues concluded that:
"Markers of abdominal adiposity showed a graded and significant association with risk of stroke/TIA, independent of other vascular risk factors. Waist circumference and related ratios can better predict cerebrovascular events than BMI."
According to a report in WebMD, Dr Tobias Back, the senior author of the study, who is based at Saxon Hospital Arnsdorf in Dresden, told the press people should keep and eye on their waistline and not let it get big:
"While gaining too much weight can present health risks, it’s even more dangerous to have the abdominal type of obesity."
Back urged everyone to stay physically active too; the researchers noticed there was a higher proportion of physically active people in the healthy group than in the stroke group. He also encouraged people to eat more healthily:
"A Mediterranean diet containing fish and olive oil can lower your risk of coronary heart disease and possibly also lower stroke risk."
Back said that as well as considering a patient’s whole vascular risk profile, doctors should use waistline measures such as the waist to hip ratio as defined by the World Health Organization (WHO) to monitor stroke risk.
The WHO estimates that about 17 million people a year die of cardiovascular diseases, particularly heart attack and strokes. A great number of these can be attributed to tobacco smoking, which increases the risk two or three-fold, while physical inactivity and poor diet are other main risk factors.
(Source: Stroke: World Health Organization: August 2008)