*4.2. Other Factors Related to Hypertension*

Our findings also revealed that the participants with a higher intake of sodium-topotassium ratio had 1.7 times higher risk of developing hypertension, which confers with the report of Park et al. [40] that sodium-to-potassium ratio and blood pressure were strongly correlated. Moreover, participants in the Hypertensive group had the highest intake of sodium (Na) and salt (NaCl), 5082.4 mg/day and 12.8 g/day, respectively, which was higher than the Japanese Society of Hypertension s recommendation of 6.0 g/day for hypertensive individuals [5]. However, because the BDHQ was designed to evaluate Japanese dietary habits and was not specific for sodium intake, we were unable to establish the relationship between salt intake, sodium intake, and hypertension in this study [57]. The current study considered that the easy-to-chew foods preferred by the older Japanese adults were processed foods with high salt content [5]. It was previously reported that the high salt intake increases BP, and excessive salt intake was one of the possible causes for the high prevalence of hypertension and stroke in Japan [5,62]. Furthermore, we also found that even if the participants in this study had a normal BMI, their BP was still higher, which was consistent with the report of the JSH 2019 that the hypertensive Japanese are often free of obesity [5]. The results of our study also suggested that the participants with a higher BMI were 1.2 times more likely to develop hypertension and/or need BP control, which was also agreeing with the JSH 2019 report that population risk for cardiovascular diseases was higher in hypertensive non-obese individuals than that in the hypertensive obese individuals [5].

Hence, the Japanese government conducted mass media-mediated public education, obligated food manufacturers to indicate salt content in food packaging, promoted nutritional labeling in school lunch/food service industries, distributed home blood pressure measurements, and required all allied health professionals to instruct patients including non-hypertensive individuals to improve their lifestyle including the balanced dietary intake, improved oral hygiene, increased physical activities (approximately 1500 step increase in the number of steps), and maintain moderate alcohol consumption. Furthermore, the Japanese government provided home-visit dental services to promote the oral health of dependent older adults and covered dental care as part of its universal health coverage [5,13]. These strategies are required to achieve the goals of reducing hypertension, CVD morbidity/mortality, and extending the healthy life expectancy of Japanese individuals.

#### *4.3. Limitation*

Several limitations must be considered when interpreting the findings of this study. First, there might have been an underestimation or overestimation of dietary intake because the BDHQ is a self-report survey designed to evaluate Japanese dietary patterns, habitual intake, cooking, and seasoning, which did not reflect the quantity of selected foods [63]. Second, the sodium-to-potassium ratio was not calculated using the urine analysis [57]. Third, we failed to find a relationship between education and living arrangements with the hypertension risk because highly educated individuals may be more knowledgeable about choosing healthy food [64], while individuals who eat alone might choose a quick and simple meal rather than a nutritionally balanced diet [65]. This might happen because we evaluated them based on their educational years rather than the educational level. Lastly, no causal relationships among dietary intake, oral health, and hypertension were established because of the observational design of the study. Hence, further studies should be conducted in the future to elucidate more on the role of oral health in nutrition.
