## 4 Discussion  
In our study, we utilized the facial landmarks to enable us to investigate the difference in the facial characteristics of hypertension patients and normal subjects. Facial landmarks extracted from the automatic extraction program will provide us with the facial feature characteristics of our subjects, whereas CIELAB color space values will provide us with the subjects' facial color characteristics. At the same time, this will enable us to make use of facial recognition technology in medical research. In this study, facial characteristics, as well as demographic characteristics, were used as variables to predict hypertension. By using the facial landmarks and CIELAB color  
Figure 4: ROC curves for LASSO using 5-fold cross-validation in the analysis of the combination of facial feature and facial color. Black lines show individual ROC curves for 5-fold cross-validation, and the red line shows the average of individual ROC curves. Figure 3: Illustration of selected variables by LASSO for both genders. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Gender** & \(n\) & **Number of Selected Variables** & **AUC (95\% CI)** & **Grading** \\ \hline Men & 376 & 18 & 0.706 (0.652–0.760) & Fair \\ Women & 723 & 18 & 0.827 (0.794–0.860) & Good \\ \hline \hline \end{tabular} AUC academic point system: 0.90–1 = excellent (A); 0.80–0.90 = good (B); 0.70–0.80 = fair (C); 0.60–0.70 = poor (D); 0.50–0.60 = fail (F).  
\end{table} 
Table 8: Calculated AUC values. system, our study revealed the role of facial characteristics in predicting the of hypertension. Our study obtained several interesting results after we statistically analyzed the associations between facial characteristics indices and hypertension together with demographic characteristics. We found that facial shape width (jaw area) and nose length in men, in addition to eye shape and nose length in women, were the most distinct facial feature differences between hypertension patients and normal individuals. For facial colors, cheek color in men, as well as forehead and nose color in women, were the most distinct facial colors between the hypertension groups and normal individuals. To find the predictors for hypertension using facial characteristics, we further analyzed our results using the LASSO method and evaluate the accuracy of the hypertension prediction model. According to our results, facial angle, eye length and angle, mouth ratio, forehead shape, nose tilting angle, forehead color, and cheek color variables were selected by the predicting model. As this study is in the exploratory stage, we only manage to explore all the variables related to hypertension. A larger and more balanced sample size is needed to formulate a predicting model thoroughly. Looking at the AUC values, the case model generated for women is the better case model with the AUC (95%CI) value of 0.827 (0.794-0.860). In comparison to women, men had a lower AUC value (AUC (95%CI) value of 0.706 (0.652-0.760)), and we assumed that it may be partly due to the low sample size. In general, both case models of men and women in the prediction of hypertension can be considered fairly well. This indicates that there might be a possibility in predicting hypertension using facial characteristics. This study examined the possibility of predicting hypertension in a non-contact method. We believed that this study can be further developed into a total unconscious screening of hypertension on a daily life basis. For example, the daily self-screening of hypertension can be performed simply by looking at the mirror which could analyze the facial characteristics of the individual. Such method can provide an alternative method to patients who were unable to monitor hypertension using labor-intensive conventional methods on a daily basis. This can also minimize health care costs through early detection of hypertension and reach a target population with minimum inconvenience to patients. At the same time, it can ensure that diagnoses of hypertension are not overlooked or discovered too late.