  Stroke poses a significant global health threat, with millions affected
annually, leading to substantial morbidity and mortality. Current stroke risk
assessment for the general population relies on markers such as demographics,
blood tests, and comorbidities. A minimally invasive, clinically scalable, and
cost-effective way to directly measure cerebral blood flow presents an
opportunity. This opportunity has potential to positively impact effective
stroke risk assessment prevention and intervention. Physiological changes in
the cerebral vascular system, particularly in response to carbon dioxide level
changes and oxygen deprivation, such as during breath-holding, can offer
insights into stroke risk assessment. However, existing methods for measuring
cerebral perfusion reserve, such as blood flow and blood volume changes, are
limited by either invasiveness or impracticality. Here, we propose a
transcranial approach using speckle contrast optical spectroscopy (SCOS) to
non-invasively monitor regional changes in brain blood flow and volume during
breath-holding. Our study, conducted on 50 individuals classified into two
groups (low-risk and higher-risk for stroke), shows significant differences in
blood dynamic changes during breath-holding between the two groups, providing
physiological insights for stroke risk assessment using a non-invasive
quantification paradigm. Given its cost-effectiveness, scalability,
portability, and simplicity, this laser-centric tool has significant potential
in enhancing the pre-screening of stroke and mitigating strokes in the general
population through early diagnosis and intervention.
