Coefficient plot - Increase gap between rows and alternative background colors in rows

Question

I have created this coefficient plot. However, I cannot increase the gap between rows. I also like to add an alternative background colour of row (like row-wise grey then white then grey ) to make it easier for the reader to read the plot. Would you please support improving its visualization?

I used the following code to create this plot.

mydf <- data.frame(
  SubgroupH=c('Age',NA,NA,NA,NA,'Marital or Union Status',NA,NA, NA, 'Place of Residence', NA, NA, 'Education', NA, NA, NA, NA,'Occupation', NA, NA, NA, NA, 'Wealth', NA, NA, NA, NA, NA, 'Reading newspaper or magazine', NA, NA, NA, 'Frequency of watching television', NA, NA, NA, 'Frequency of  listening radio', NA, NA, NA ),
  Subgroup=c(NA,'15-19','20-29','30-39','40-49', NA, 'Currently Married or Union', 'Never Married or Union','Formally Married or Union', NA, 'Rural', 'Urban', NA, 'Higher', 'Secondary', 'Primary', 'No eduction', NA, 'Not working', 'Professional/technical/managerial/services', 'Agriculture', 'Skilled/unskilled manual', NA, 'Poorest', 'Poorer', 'Middle','Richer', 'Richest',  NA, 'Not at all', 'Less than once a week', 'At least once a week', NA, 'Not at all', 'Less than once a week', 'At least once a week', NA, 'Not at all', 'Less than once a week', 'At least once a week'),
  AdjustedOR=c(NA,1,'2.76 (2.49-3.07)','3.68 (3.26-4.15)','4.61 (4.06-5.23)',NA,1,'1.03 (0.94-1.13)', '1.26 (1.04-1.54)', NA, 1,'1.12 (1.04-1.21)', NA, 1, '1.42 (1.30-1.56)', '2.09 (1.85-2.36)', '2.20 (1.93-2.49)', NA, 1, '1.39 (1.25-1.54)', '1.37 (1.24-1.51)', '1.55 (1.39-1.72)', NA, 1, '0.91 (0.84-0.99)', '0.77 (0.71-0.84)', '0.72 (0.65-0.79)', '0.61 (0.54-0.69)', NA, 1, '1 (0.91-1.10)', '0.92 (0.85-0.998)', NA, 1, '1.19 (1.07-1.31)', '1.29 (1.19-1.40)', NA, 1, '1.19 (1.09-1.30)', '1.13 (1.05-1.21)'),
  OddsRatio=c(NA,1,2.76,3.68,4.61, NA,1,1.03, 1.26, NA, 1,1.12, NA, 1, 1.42, 2.09, 2.20, NA, 1, 1.39, 1.37, 1.55, NA, 1, 0.91, 0.77, 0.78, 0.61 , NA, 1, 1,0.92, NA, 1,1.19,1.29, NA, 1, 1.19, 1.13),
  ORLower=c(NA,NA,2.49,3.26,4.06,NA,NA,0.94, 1.04, NA, NA,1.04, NA, NA, 1.30,1.85, 1.93, NA, NA,1.25, 1.24, 1.39, NA, NA, 0.84, 0.71, 0.65, 0.54, NA, NA, 0.91, 0.85, NA, NA, 1.07, 1.19, NA, NA,1.09, 1.05),
  ORUpper=c(NA,NA,3.07,4.15,5.23,NA,NA,1.13, 1.54, NA, NA,1.21, NA, NA, 1.56, 2.36, 2.49, NA, NA, 1.54, 1.51,1.72, NA, NA, 0.99, 0.84, 0.79, 0.69, NA, NA, 1.10, 0.998, NA, NA, 1.31, 1.40, NA, NA, 1.30,1.21),
  Pvalue=c(NA,NA,'< 0.001','< 0.001','< 0.001', NA,NA, 0.518, 0.021, NA, NA, 0.003, NA, NA, '< 0.001', '< 0.001', '< 0.001', NA, NA, '< 0.001', '< 0.001', '< 0.001', NA, NA, 0.029, '< 0.001','< 0.001','< 0.001', NA, NA, 0.993, 0.045, NA, NA, '< 0.001','< 0.001',NA, NA, '< 0.001', 0.002),  
  stringsAsFactors=FALSE )

#png('temp.png', width=8, height=4, units='in', res=400)

rowseq <- seq(nrow(mydf),1)
par(mai=c(0.7,0,0,0))
plot(mydf$OddsRatio, rowseq, pch=15,
     xlim=c(-0.8,6.2), ylim=c(0,42),
     xlab='', ylab='', yaxt='n', xaxt='n',
     bty='n')
axis(1, seq(0.5, 5,by=0.5), cex.axis=1)

segments(1,-1,1,40.20, lty=3, )
segments(mydf$ORLower, rowseq, mydf$ORUpper, rowseq)

mtext('Adjusted Odds Ratio (95% CI)', 1, line=2, at=1.2, cex=1, font=2)

text(-1,42, "Factors", cex=1.4, font=2, pos=4)
t1h <- ifelse(!is.na(mydf$SubgroupH), mydf$SubgroupH, '')
text(-1,rowseq, t1h, cex=1.3, pos=4, font=2)
t1 <- ifelse(!is.na(mydf$Subgroup), mydf$Subgroup, '')
text(-0.98,rowseq, t1, cex=1.3, pos=4)

text(4.6,42, "Adjusted Odds Ratio (95% CI)", cex=1.4, font=2, pos=4)
t2 <- ifelse(!is.na(mydf$AdjustedOR), format(mydf$AdjustedOR,big.mark=","), '')
text(6, rowseq, t2, cex=1.3, pos=2)

text(6,42, "P-value", cex=1.4, font=2, pos=4)
t4 <- ifelse(!is.na(mydf$Pvalue), mydf$Pvalue, '')
text(6,rowseq, t4, cex=1.3, pos=4)