As we continue to discuss and become informed about stroke, it is quite evident that the immune system plays a role in both pre stroke and post stroke conditions. As discussed last week by specialist Juliet, we have been able to demonstrate that induced immunodepression after an ischemic stroke event has both positive and negative effects in rodents. While it increases susceptibility to infection, it can potentially suppress autoagressive responses catalyzed by inflammation that are very possible to occur with the formation of lesions after an ischemic brain infarction. Diving into that article really got me wondering about the potential connection between our immune systems and stroke. One of the best ways to see this connection is to take a look at a study done by the University of Kentucky's Department Neurology in which they review "Stroke in HIV Infection and AIDS". If we take away the immune system, do stroke risk-factors change?
In this study, the doctors from the University of Kentucky analyzed multiple cohort and case-control studies that were completed from the United States, Europe, Asia, Australia, and most importantly, Africa. With the analysis of each study, it has been made statistically significant that advanced HIV infection and AIDS lead to "opportunistic infections, intracranial malignancies, marantic endocarditis, cachexia & dehydration, and coagulation abnormalities" which lead to significantly increased risk for either type of stroke in younger populations (50 and younger) not otherwise significantly affected by stroke (Dobbs 1263). The researchers crunched numbers from these cohort studies and point out (just to name a few) that the prevalence of HIV in young stroke patients from KwaZulu Natal, Africa is 16% while it is around 6% (lower yet still significant) in Cape Town, South Africa (Dobbs 1264). In addition to the significant prevalence of HIV/AIDS in these young stroke populations, the researchers very animately declare that instead of the "typical risk factors for ischemic stroke [hypertension, diabetes, hyperlipdemia, and smoking]" we see significant levels of infectious meningitis/vasculitus (28%), coagulopathy (19%), cardioembolism (14%), and multiple etiologies (11%) as risk factors for stroke (Dobbs 1264).
So now we can see the difference in the dynamic that HIV/AIDS both bring to induce similar results in young stroke patients that typical stroke patients experience from a completely different set of risk factors. The researchers bring to light that these similar results come from HIV-associated vasculopathy: Small-vessel vasculopathy as well as medium/large vessel vasculopathy to vessels in the Central Nervous System (Dobbs 1266-1267). In short, altered (deficient) levels of CD4 cells and Protein S help to set the table for conditions that promote alternative vasculopathy which leads to "small-vessel-wall thickening, perivascular space dilation, rarefaction and pigment deposition" as well as "medium-vessel occlusion or significant stenosis of the extracranial carotid artery" (Dobbs 1267). To bring all of these findings together, the researchers point out that the mean age of HIV-infected stroke patients is 33.4 years (19-74 range) while non HIV-infected stroke patients averaged the age of 64 years (17-96 range), (Dobbs 1267).
In previous discussions we've seen and defined typical risk factors for both ischemic and hemorrhagic strokes. Now we see what happens when the immune system is pretty much eliminated from the equation. What do you think about these findings? More importantly, what other links can be found between either type of stroke, inflammation, and the immune system?
Dobbs, Michael, and Joseph Berger. "Stroke in HIV Infection and AIDS." Expert Reviews. 7.10 (2009): 1263-1271. Web. 6 Oct. 2013. <http://www.osuem.com/downloads/resources/AIDSandstroke.pdf>.
It's not a huge surprise that patients with HIV/AIDS have risks of stroke but what really gets me is the different risk factors that comes with HIV/AIDS related stroke (as compared to 'normal' risk factors). With HIV/AIDS patients, infectious bacteria & viruses are often the cause of strokes.
ReplyDeleteThis research article also makes me think about how the post-stroke immunodepression is altered in HIV/AIDS patients. Their immune system is already compromised so does their system become further depressed? Furthermore, I wonder if HIV/AIDS stroke patients have less damage to the brain than 'normal' stroke patients due to the lack of a post-stroke immune response.
This is a very interesting topic. Like Sarah said, it does make sense that HIV/AIDS patients have an increased risk of stroke (among many other things). However, the findings of this research still seem surprising.
ReplyDeleteThe researchers state that they see alternative risk factors (such as infections) as more important in determining a person's risk for stroke than traditional risk factors. To me, it seems like the prevalence of cardiovascular disease or just cardiovascular problems (such as hypertension) are much less common in developing countries. CVD seems to be mostly a first world problem. This makes me wonder how much I can trust the statement that things such as infections are more important in determining a person's risk of stroke than cardiovascular risk factors. Although, it's hard to say. In this study, they are looking at a very specific group of people. Those with HIV/AIDS in sub-Saharan Africa.