In case of total marks in anatomy, MRR, and RRTi were found to have statistically significant negative correlation with academic performance only in males.
Again in males, RRTi was negatively correlated with practical IA but not statistically significant (r = -0.330, P = 0.057).
However, in case of theory IA, significant negative correlations are observed with MRR, SDNN, RMSSD, NN50, pNN50, RRTi, and TINN in males.
A detailed ARI and RRTI history was taken in the selected population.
Table 1 shows the number of cases examined, the methemoglobin levels (met-Hb), the average cytochrome [b.sub.5] reductase activity, and the number and percent of RRTI cases for each nitrate concentration.
Abbreviations: cyto, cytochrome [b.sub.5] reductase activity; +ve, cases with a history of RRTI.
Regression analysis between percent RRTI and met-Hb indicated a high correlation coefficient ([R.sup.2] = 0.803) at 95% significance level with a p-value of 0.04.
We observed a high percentage (40-82%) of RRTI at various nitrate concentrations in drinking water in children up to 8 years of age.
A significant positive coefficient of correlation (0.731), a high coefficient of regression ([R.sup.2] = 0.803), and p [is less than] 0.05 indicate a probable cause-effect relationship between high met-Hb concentration and RRTI. In fact, these high methemoglobin levels are primarily caused by high nitrate concentrations in drinking water, and there is ample evidence (10,24,25) to indicate that higher nitrate concentration in drinking water causes methemoglobinemia.