Background: Forest fires in South Asia periodically led to widespread haze for a few months per year in neighbouring countries. The magnitude of health effects of short-term haze exposure remains to be studied, but acute psychosomatic symptoms have been reported in previous studies during acute haze crises. We investigated the effect of haze exposure on cerebral haemodynamics and psychosomatic symptoms.

Method: We enrolled 74 healthy volunteers for this study. Baseline transcranial doppler (TCD) was performed by a trained sonographer in an indoor, air-conditioned environment. Each subject then had a second TCD performed by a second sonographer after thirty minutes outdoors. The prevailing level of pollutant standards index (PSI) was obtained by measurements captured by the Singapore National Environmental Agency. Any new symptoms experienced by the participants were recorded by means of a standardized questionnaire. Appropriate statistical analyses were employed to compare cerebral hemodynamics between the symptomatic and asymptomatic groups of participants.

Results: Our subjects had a median age of 30 (IQR 26-34) years, of which 60.8% were female. 35 subjects developed psychosomatic symptoms. There was a significantly reduced pulsatility index (PI) in both the left and right middle cerebral arteries (MCA) for the symptomatic group compared to the asymptomatic group (left MCA: 0.85±0.10 vs 0.93±0.07 p<0.001; right MCA: 0.84±0.13 vs 0.94±0.08, p<0.001). In the symptomatic group, mean pulsatility index (PI) decreased from 0.90±0.12 to 0.84±0.10 (p<0.008) after haze exposure. There was a moderate negative correlation between PI and number of psychosomatic symptoms experienced (r=0.519,p<0.001). 

Conclusion: Significant differences in cerebral haemodynamics as demonstrated by TCD exist after short-term haze exposure. The changes in PI highlight the cerebral vasodilatory effect of haze particles, which may play a role in causing psychosomatic symptoms. These findings correlate with severity  of haze exposure (PSI) and psychosomatic symptoms experienced. The prognostic implications and health effects of these findings warrant further study.

PSYCHOSOMATIC SYMPTOMS DURING SOUTH EAST ASIAN HAZE CRISIS ARE RELATED TO CHANGES IN CEREBRAL HEMODYNAMICS