Evaluation of Vasomotor Reactivity by Transcranial Doppler Sonography: Age and Sex Related Differences in Breath Holding Index in Iranian Population

Background: The assessment of cerebral vasoreactivity can provide information regarding the reserve capacity of cerebral circulation. Reduction of this property has been found in association with situations predisposing one toward cerebrovascular disease. In this study, we defined the vasoreactivity of brain vesseles according to age and sex of the patients.
 Methods: In this descriptive study, 289 healthy subjects (without hypertension, diabetes mellitus, obesity, smoking, CHF, CHD,) were admitted from January 2004 to June 2004. The population was divided to four groups, according to age and sex (women and men more and less than 30). After determination of each patient’s flow velocity of middle cerebral artery (MCA) by mean of a transcranial doppler instrument (TCD), before and after 30s apnea, breath holding index (BHI) was calculated. Data was analyzed, using SPSS software.
 Results: BHI was significantly higher in women than men (0.918±0.40 versus 0.637±0.22; P<0.001). BHI was significantly lower in older (age > 30 ) women (0.812±0.31) than in younger ( ≤ 30 years ) women (0.995±0.44; P<0.001) but there was no significant difference between older (age > 30 ) men (0.62±0.23 ) and younger ( ≤ 30 years ) men (0.65±0.20; P > 0.05).
 Conclusion: The average of BHI was lower in men than in women in total and in all age subgroups. BHI was relatively constant in all age subgroups in men but there was significant decline in BHI by increasing age in women. So despite of many physiologic changes related to aging, vasomotor reactivity remains relatively constant in men but decreases in women. Findings of our study suggest that changes of cerebrovascular vasomotor reactivity in healthy subjects may be related to aging, but they are probably mainly influenced by sex.
 Keywords: vasomotor reactivity, BHI, TC