## 4 Discussion  
Compared to previous findings, the smokers in this study exhibited a significant increase in the IMTs of both the RCA and the LCA. The IMTs of the two carotid arteries increased insignificantly as the duration of smoking increased, and decreased as the frequency of smoking increased. The studied parameters of both smokers and non-smokers \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Carotid Artery Thickness (mm)**} \\ \cline{2-7}  & \multicolumn{3}{c}{**Smokers**} & \multicolumn{3}{c}{**Non-Smokers**} \\ \cline{2-7}  & \(\leq\)**0.6** & **0.7–0.8** & **0.9\(\geq\)** & **0.7–0.8 (10)** & **0.9\(\geq\)** \\  & **(5)** & **(10)** & **(4)** & & **(4)** \\ \hline TC mg/dL & 127.2 \(\pm\) 45.4 * & 172.9 \(\pm\) 30.8 * & 167.7 \(\pm\) 39.8 & 146.6 \(\pm\) 30.5 & 176.2 \(\pm\) 47.02 & 149.2 \(\pm\) 27.7 \\ \hline TG mg/dL & 239.4 \(\pm\) 335.2 & 245.5 \(\pm\) 88.9 & 241.4 \(\pm\) 105.3 & 188.4 \(\pm\) 143.5 & 321.4 \(\pm\) 308.8 & 241.1 \(\pm\) 118.7 \\ \hline HDL-C mg/dL & 42.9 \(\pm\) 17.8 & 40.1 \(\pm\) 7.7 & 44.1 \(\pm\) 7.7 & 45.2 \(\pm\) 15.1 & 44.8 \(\pm\) 18.4 & 38.23 \(\pm\) 17.4 \\ \hline LDL-C mg/dL & 48.2 \(\pm\) 16.30 & 64.30 \(\pm\) 33.49 & 75.3 \(\pm\) 13.79 & 68.83 \(\pm\) 29.38 & 85.63 \(\pm\) 30.27 & 62.75 \(\pm\) 17.86 \\ \hline TC/HDL ratio & 3.13 \(\pm\) 0.87 & 4.53 \(\pm\) 1.54 & 3.8 \(\pm\) 0.43 & 3.5 \(\pm\) 1.36 & 4.16 \(\pm\) 0.97 & 4.47 \(\pm\) 1.73 \\ \hline \hline \end{tabular}  
* There was significant increase in the triglycerides concentration of the smokers with the increase of the IMT of the carotid arteries
* (\(p\)-value = 0.032).  
\end{table} 
Table 6: Mean values of studied parameters in smokers and non-smokers, according to carotid artery thicknesses. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**BMI**} \\ \cline{2-7}  & \multicolumn{3}{c}{**Smokers**} & \multicolumn{3}{c}{**Non-Smokers**} \\ \cline{2-7}  & **Normal** & **Overweight** & **Obese** & **Normal** & **Overweight** & **Obese** \\  & **(7)** & **(6)** & **(6)** & **(13)** & **(11)** & **(11)** \\ \hline TC/HDL ratio & 3.95 \(\pm\) 2.5 & 4.02 \(\pm\) 0.71 & 4.11 \(\pm\) 0.94 & 3.58 \(\pm\) 1.13 & 4.35 \(\pm\) 1.85 & 3.47 \(\pm\) 0.88 \\ \hline RCA (mm) & 0.61 \(\pm\) 0.13 * & 0.78 \(\pm\) 0.12 ** & 0.76 \(\pm\) 0.12 *** & 0.58 \(\pm\) 0.2 & 0.67 \(\pm\) 0.13 & 0.69 \(\pm\) 0.18 \\ \hline LCA (mm) & 0.60 \(\pm\) 0.13 * & 0.77 \(\pm\) 0.10 * & 0.73 \(\pm\) 0.13 *** & 0.58 \(\pm\) 0.15 & 0.68 \(\pm\) 0.11 & 0.68 \(\pm\) 0.16 \\ \hline \hline \end{tabular}  
* Smokers’ BMIs increased TC, HDL-cholesterol, TG and the TC/HDL ratio insignificantly, whereas it increased both right and left carotid artery IMTs significantly. Non-smokers’ BMIs had an insignificant effect on all the parameters studied: The significant differences between the studied mean values were associated with IMT of the carotids arteries as follows:
* (\(p\)-value = 0.005),
* (\(p\)-value = 0.021),
* (\(p\)-value = 0.016),
* (\(p\)-value = 0.027) and
* (\(p\)-value = 0.05).  
\end{table} 
Table 5: _Cont._were affected variably by both age and BMI. Carotid artery IMTs play a crucial role in determining the LP, specifically the plasma HDL-C, blood cholesterol and cholesterol ratio. A significant, positive effect of smoking on TC, TG and LDL-C was reported in most of the previous studies [4, 11, 12, 13]. [PERSON] et al. (2006) found that the TC, LDL-C and non-HDL-C were elevated notably in the blood of smokers, compared to non-smokers [14]. With regard to the effect of smoking on the concentration of HDL-C in the blood, most previous studies demonstrated that smoking significantly decreased the level of HDL-C in the blood [15, 16, 17]. To some extent, the findings of this study are similar to those of previous research, as this work reported that smoking was associated with insignificant increases in the TC, TG and the blood cholesterol ratio, and with an insignificant decrease in HDL-C. It is well known that smoking is strongly correlated with high TC/HDL and also LDL/HDL ratios.