Obesity significantly associated with thinner cerebral cortex, particularly in under-65s
A recent analysis of 1,289 individuals across normal, overweight and obese Body Mass Index (BMI) ranges demonstrated that higher BMI and waist circumference values were significantly associated with thinner brain cortices.
In the study, researchers analyzed data from the population-based prospective cohort Northern Manhattan MRI substudy, using multivariable linear and logistic regression models adjusted for sociodemographics, health behaviours, and vascular risk factors and tested interactions with age, sex, and race/ethnicity. [Neurology 2009;73:1774-1779] The study participants’ average age at baseline was 64 years; 60 percent of participants were female and 66 percent were Caribbean Hispanic. Their BMI and waist circumference (WC) were measured at the beginning of the study, while MRI brain scans were conducted at an average of 6 years after enrolment in the study. [Neurology 2019, doi: 10.1212/WNL.0000000000007966]
A total of 346 participants had normal weight (BMI, <25 kg/m2), 571 were overweight (BMI, 25–30 kg/m2), and 372 were obese (BMI, ≥30 kg/m2). In the normal-weight group (54 percent female), the average WC was 33 inches. In comparison, average WC was 36 inches in the overweight group (56 percent female) and 41 inches in the obese group (73 percent female).
Of note, greater BMI and WC were significantly associated with thinner cortices as assessed by MRI brain scans (BMI: odds ratio [OR], −0.089; 95 percent confidence interval [CI], −0.153 to −0.025; WC: OR, −0.103; 95 percent CI, −0.169 to −0.037). After adjusting for other factors that could affect the cortex, such as high blood pressure, alcohol consumption and smoking, obese participants were found to have thinner cortices than normal-weight individuals (OR, −0.207; 95 percent CI, −0.374 to −0.041). “These associations were particularly evident for those younger than 65 years of age,” noted the researchers.
In overweight participants, every unit increase in BMI was associated with a 0.098 mm reduction in cortical thickness. In obese participants, every extra BMI unit was associated with a 0.207 mm cortical thickness reduction.
Having a thinner cerebral cortex has been tied to an increased risk of Alzheimer’s disease. [Neurobiol Aging 2018;61:238-244] “In normal ageing adults, the overall thinning rate of the cortical mantle is between 0.01 mm and 0.10 mm per decade. Our results would indicate that being overweight or obese may accelerate ageing in the brain by at least a decade,” wrote the researchers.