THE INFLUENCE OF RACIAL AND ENVIRONMENTAL-FACTORS ON EEG PHOTOPAROXYSMAL RESPONSES IN ZIMBABWE

Objective - This study examined the influences of environmental and ra cial factors on the incidence of EEG photoparoxysmal responses (PPRs) to intermittent photic stimulation (IPS) in a multi-racial population exposed to seasonal variations in sunshine intensity. Materials and me thods - The records of patients referred for EEG examination in Harare , Zimbabwe were screened for the presence of PPRs to IPS. The age, sex and racial classification of patients manifesting PPRs were studied. The relationship between sunshine duration and intensity and the frequ ency of PPRs was also studied. Results - EEG records of 16,496 patient s referred for EEG examination were studied. Of these. 136 patients (0 .8%) showed PPRs to photic stimulation. The highest age-specific PPR ( 2.0%) occurred in the 16-20 year age group. The race-specific PPRs wer e 1.5% for white patients, 1.18% for Asian patients. 0.36% for colored patients and 0.09% for black patients (chi(3)(2)=95.21, P=0.001). The incidence of PPRs did not show any significant variation with the mea n monthly sunshine duration (P=0.8254) or with the mean monthly sunlig ht radiation (P=0.2631), Conclusion - The findings of this study suppo rt a role for genetic rather than environmental factors in the relativ e rarity of PPRs in black Zimbabweans.