Body Fat Distribution Should Be Considered in Risk for Major Types of Stroke

BMI and waist circumference have contrasting associations with risk of various types of stroke.

The independent and contrasting associations of body mass index (BMI) and waist circumference with the risk for various types of stroke have suggested the importance of considering body fat distribution to stroke risk, according to the results of a large-scale, prospective study published in JAMA Network Open.

Uncertainty persists regarding the independent association of general adiposity (BMI) and central adiposity (waist circumference) with major forms of stroke. For the study, researchers sought to establish the independent associations of 2 types of adiposity with risk for ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH).

Between 2006 and 2010, adults who had not experienced a prior stroke at recruitment in England, Scotland, and Wales were recruited into the current study from the UK Biobank. All participants were followed up through linkage with electronic medical records. All of the data obtained were analyzed between September 2021 and September 2022.

A total of 490,071 participants were enrolled in the study. Overall, 54.6% of the participants were women and 94.2% were White. The mean participant age was 56.5±8.1 years. During a median of 12.0 years (range, 11.2-12.7 years), a total of 7117 incident ischemic strokes, 1391 ICHs, and 834 SAHs were reported.

[S]ome adverse correlate of low BMI may be associated with an increased risk of ICH and SAH … and this warrants further investigation.

The researchers found that after mutual adjustment for waist circumference, BMI demonstrated no independent association with ischemic stroke (hazard ratio [HR] per 5-unit higher BMI, 1.04; 95% CI, 0.97-1.11), but was inversely associated with ICH (HR, 0.85; 95% CI, 0.74-0.96) and SAH (HR, 0.82; 95% CI, 0.69-0.96).

Waist circumference, which was adjusted for BMI, was positively associated with ischemic stroke (HR per 10-cm higher waist circumference, 1.19; 95% CI, 1.13-1.25) and ICH (HR, 1.17; 95% CI, 1.05-1.30), but was not associated with SAH (HR, 1.07; 95% CI, 0.93-1.22).

Approximately 80% of the positive associations of BMI and waist circumference with ischemic stroke were explained by a set of well-established cardiovascular (CV) risk factors (ie, systolic blood pressure, low-density lipoprotein cholesterol, triglycerides, and hemoglobin A1c), with these associations only minimally reduced following additional adjustment for C-reactive protein, estimated glomerular filtration rate, alanine aminotransferase, and uric acid.

Study limitations include the fact that the associations were not evaluated by stroke subtype, which is important, with some evidence suggesting that the associations with other major CV factors that are linked to risk may vary according to stroke subtype. Additionally, because the majority of individuals in the study population were White, little power existed to evaluate the association in other racial groups, which may have different distributions of body fat and CV risk factors.

The researchers concluded, “Several intermediate factors for the associations of adiposity with stroke types were identified, but none explained the inverse associations with BMI. This suggests that some adverse correlate of low BMI may be associated with an increased risk of ICH and SAH — or, equivalently, some protective correlate of high BMI may be associated with reduced risk of these stroke types — and this warrants further investigation.”

Disclosure: One of the study authors has declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of the author’s disclosures.

References:

Pillay P, Lewington S, Taylor H, Lacey B, Carter J. Adiposity, body fat distribution, and risk of major stroke types among adults in the United Kingdom. JAMA Netw Open. Published online December 14, 2022. doi:10.1001/jamanetworkopen.2022.46613