Obesity paradox in subarachnoid hemorrhage: a systematic review

Abstract

As the number of obese people is globally increasing, reports about the putative protective effect of obesity in life-threatening diseases, such as subarachnoid hemorrhage (SAH), are gaining more interest. This theory-the obesity paradox-is challenging to study, and the impact of obesity has remained unclear in survival of several critical illnesses, including SAH. Thus, we performed a systematic review to clarify the relation of obesity and SAH mortality. Our study protocol included systematic literature search in PubMed, Scopus, and Cochrane library databases, whereas risk-of-bias estimation and quality of each selected study were evaluated by the Critical Appraisal Skills Program and Cochrane Collaboration guidelines. A directional power analysis was performed to estimate sufficient sample size for significant results. From 176 reviewed studies, six fulfilled our eligibility criteria for qualitative analysis. One study found paradoxical effect (odds ratio, OR = 0.83 (0.74-0.92)) between morbid obesity (body mass index (BMI) > 40) and in-hospital SAH mortality, and another study found the effect between continuously increasing BMI and both short-term (OR = 0.90 (0.82-0.99)) and long-term SAH mortalities (OR = 0.92 (0.85-0.98)). However, according to our quality assessment, methodological shortcomings expose all reviewed studies to a high-risk-of-bias. Even though two studies suggest that obesity may protect SAH patients from death in the acute phase, all reviewed studies suffered from methodological shortcomings that have been typical in the research field of obesity paradox. Therefore, no definite conclusions could be drawn.

Obesity and Stroke: Does the Paradox Apply for Stroke?

“…As we previously mentioned, obesity predisposes an increased risk of suffering cardiovascular and systemic diseases, such as stroke and other diseases. 29,33,34,[47][48][49] It is associated with premature mortality; and, in multiple studies, a higher risk of cardiovascular disease incidence has been demonstrated in underweight adults or just overweight (but not obese) patients. As a result, there is no clear evidence of a higher prevalence or incidence of stroke in those with an obesity diagnosis.…”

Body Mass Index and Leptin Levels in Serum and Cerebrospinal Fluid in Relation to Delayed Cerebral Ischemia and Outcome after Aneurysmal Subarachnoid Hemorrhage

“…The two largest studies were based on patient registries yielding considerable case numbers but came to diverging results with one trial documenting reduced in-hospital mortality and the other rejecting the obesity paradox [6,10]. The methodological integrity of these trials was critically addressed in a recent systematic review [27]. It remains possible that a protective effect of mild obesity exists -unspeci c to SAH or stroke -potentially related to overall caloric reserves which may prove advantageous in the light of long ICU stays [18,23].…”

“…A single trial in SAH patients described a lower risk of DCI and DCI-related infarction associated with elevated BMI [29]. Nonetheless, the results of a systemic review addressing this obesity paradox in SAH remained inconclusive as most trials suffered restrictions in design, resulting in limited external validity [27].…”

Dyslipidemia and rupture risk of intracranial aneurysms—a systematic review

“…However, hypercholesterolemia was associated with a seemingly paradoxical 40% reduction in the risk of aSAH in a review of case-control studies [12]. Furthermore, a recent systematic review on obesity and aSAH indicated a reduced risk of aneurysm rupture with increasing BMI but concluded that this seemingly paradoxical relation remains to be studied in more detail [33]. The same group performed a systematic review on cholesterol as a risk factor for aSAH and concluded that elevated TC levels increased the risk of aSAH among men [26].…”