Hemodynamic and Functional Characteristics of the Cerebral Circulation in Obesity

Obesity, defined by the World Health Organization (WHO) as a body mass index of 30 or higher, is reaching epidemic proportions worldwide, with some 2.8 million attributable deaths annually. Initially linked to countries with higher incomes, it is now a serious health problem in countries with medium and low incomes.

The increase in body mass index from overweight to obesity is linearly correlated with an increase in coronary and cerebral vascular events, as well as death from vascular causes. Apart from the fact that obese patients are at higher risk of having classic vascular risk factors (independently associated with atherosclerosis and a risk of vascular events), the evident linear relationship between obesity and vascular pathology suggests the existence of pathophysiological mechanisms related to the accumulation of fat that cause structural and functional damage to the vascular system.

Adipokines are a group of pro-inflammatory peptides specifically secreted by fat tissue that have been linked to inflammatory activity, endothelial dysfunction, and insulin resistance in overweight and obese conditions. From these studies, a wealth of knowledge is drawn on the relationship of obesity with large-vessel atherosclerosis; but yet, few studies have focused on the particular relationship of obesity on the cerebral vasculature, despite the strong epidemiological relationship between obesity in middle age (and vascular risk factors in general) and cognitive deficits and vascular dementia in the elderly, possibly driven to a large extent by cerebral small vessel disease.

Small vessel disease (including both radiological signs on MRI in the form of white matter lesions, lacunar infarcts and/or cognitive impairment, and vascular dementia/Alzheimer's disease) have been positively correlated in several retrospective and prospective studies with the Gosling index or pulsatility index (PI) obtained by transcranial Doppler study in the middle cerebral artery. In recent years, much importance has been attached to the potential deleterious impact that small cerebral vessel disease in middle ages may have on degenerative brain diseases over 60 years of age, however, we have not identified a specific study of haemodynamic factors of cerebral circulation in middle-aged patients.

Obese patients with an indication for bariatric surgery constituted, in our opinion, an excellent model for the study of these potential haemodynamic factors (surrogate markers of subclinical cerebrovascular disease) in two ways: by comparing them with normal-constituted volunteers; as well as comparing them with themselves once they achieve an effective reduction in their body weight after surgery.