Adiposity is not generally a risk factor for stroke
Abdominal girth is decisive
Professor Tobias Back MD is medical director of the Clinic for Neurology and Neurological Intensive Medicine in Arnsdorf, Germany.
Being the initiator of the first large-scale European case-control study on abdominal fat mass and stroke risk he presented the study results at the annual congress of the European Neurological Society, held in June in Nice, France.
Dr Back and his research team were able to demonstrate that in overweight patients it is not the body mass index (BMI) that counts when assessing stroke risk but solely abdominal girth. ‘There had only been insufficient studies that analysed the fat distribution pattern of stroke patients. The few available preliminary data were collected in the US. Now we are proud to say that we were the first Europeans to present meaningful data that show that abdominal adipositas is the sole independent risk factor associated with cerebrovascular stroke,’ he explained.
Funded by the German Ministry for Education and Research, the research project was conducted in Mannheim and Heidelberg, Germany, between February 2005 and January 2006. ‘We took great pains to assemble a suitable regional cohort of regular people. In the end we had 379 stroke patients and a control group twice that size in order to optimise the statistical relevance of our results. Average patient age was 65.’
The researchers measured the waist-to-hip ratio (WHR) by taking the abdominal girth at the navel and dividing the result by the circumference of the hip at the hip bone. Abdominal adipositas is a value defined by the World Health Organisation (WHO): in men a value above 1.00 is considered pathological, in women a value of 0.85. The WHR is more precise than the body mass index (BMI): ‘The BMI does not differentiate fat mass and muscle mass. That means a person’s individual physical state is not taken into account. The waist-to-hip ratio on the other hand is more predictive since this adipositas marker identifies visceral (abdominal) fat mass independent of body height and physique. Even more: our study clearly shows that the BMI is not an independent stroke risk factor,’ Dr Back emphasised.
‘The analysis of our data demonstrated that, after adjustment for factors such as hypertension, smoking, physical inactivity, or diabetes, pathological abdominal girth was the sole indicator for increased risk of stroke, with the risk being four to seven times higher and women being in general slightly more at risk than men.’
But why is abdominal fat so dangerous? Is it a certain type of fat that builds up around the abdomen, the so-called visceral fatty tissue that determines abdominal girth? ‘Intra-abdominal fat mass has crucial implications for a body’s fat and carbohydrate metabolism since it is particularly that kind of fat mass that causes free fatty acids, cytokines and hormones to enter the portal circulation and thus increases the risk of metabolic syndrome or diabetes.’
Consequently, with regard to stroke the Mannheim-Heidelberg Stroke Study arrives at very similar conclusions in a large-scale international study, which in 2005 showed the risk of myocardial infarction to be associated with abdominal adipositas.
‘Adipositas – both in children and in adults – will become one of the major health issues,’ Dr Back prophesised. ‘The number of people in industrialised countries that develop a metabolic syndrome is increasing steadily. We should therefore expect the number of patients with a highly unfavourable vascular risk profile to skyrocket over the coming decades. We urgently require additional studies that not only explore the association between abdominal girth and increased stroke risk but that also look at how the treatment of adipositas, particularly abdominal weight loss, decreases the risk of stroke and myocardial infarction.’
01.09.2008
