Association between socioeconomic factors and urinary sodium-to-potassium ratio: the Nagahama Study

Comparison between 24-hour diet recall and 24-hour urine collection for estimating sodium and potassium intakes and their ratio among Korean adults

BACKGROUND/OBJECTIVES

This study aimed to compare 24-h diet recall (DR) and 24-h urine collection (UC) for estimating sodium and potassium intakes and their ratio (Na/K), identifying factors associated with sodium and potassium intakes and Na/K, and identifying those who were likely to underestimate sodium and potassium intakes by DR.

SUBJECTS/METHODS

A total of 640 healthy adults aged 19-69 yrs completed a questionnaire survey, salty taste assessment, anthropometric measurement, two 24-h DRs, and two 24-h UCs.

RESULTS

The mean sodium and potassium intakes and Na/K were 3,755 mg/d, 2,737 mg/d, and 1.45 according to DR, and 4,145 mg/d, 2,812 mg/d, and 1.57 according to UC, with percentage differences of -9.4%, -2.7%, and -7.6% in the values between the two methods, respectively. Men, older adults, smokers, obese individuals, those who consumed all the liquid in the soup, and those who were found to be salty in the salty taste assessment consumed significantly more sodium; older adults, the heavy- activity group, and obese individuals consumed more potassium; and men, younger adults, smokers, and obese individuals had a significantly higher Na/K, according to UC. Compared with UC, DR was more likely to underestimate sodium intake in older adults, smokers, obese individuals, those who consumed all the liquid in the soup, and those who consumed eating-out/delivery food at least once a day, and potassium intake in older adults, the heavy-activity group, and obese individuals.

CONCLUSIONS

The mean sodium and potassium intakes and Na/K estimated by DR were comparable to those measured by UC. However, the association of sodium and potassium intakes with sociodemographic and health-related factors showed inconsistent results when estimated by DR and UC. Factors influencing the underestimation of sodium intake by DR compared to UC should be further investigated.

Association between urinary sodium-to-potassium ratio and home blood pressure and ambulatory blood pressure: the Ohasama study

OBJECTIVE

No studies have demonstrated the association between urinary sodium-to-potassium (Na/K) ratio and all out-of-office blood pressure (BP) [home morning and evening BP (self-measured at home), and 24-h, daytime, and night-time ambulatory BP] in the same cohort. We aimed to assess, which type of out-of-office BP is more strongly associated with urinary Na/K ratio in the general population.

METHODS

This cross-sectional study was conducted in the general population of Ohasama, Japan. Home and ambulatory BP levels were measured, and 24-h urine samples were obtained from 875 participants (men, 25.5%; mean age, 60.1 years). The urinary Na/K ratio in the 24-h urine samples was calculated.

RESULTS

The median (interquartile range) urinary Na/K ratio was 4.19 (3.36-5.26). Significant positive trends of home morning, home evening, 24-h, and daytime SBP were observed across quartiles of urinary Na/K ratio (trend P ≤ 0.041; adjusted mean values between Q1 and Q4 of urinary Na/K ratio: 121.0-125.5 mmHg for home morning, 120.1-123.8 mmHg for home evening, 121.6-123.4 mmHg for 24-h, 127.5-129.5 mmHg for daytime). Urinary Na/K ratio was not significantly associated with office or night-time SBP and nocturnal BP fall (trend P ≥ 0.13). In the model with both home morning or evening SBP and daytime SBP, only home SBP was significantly associated with urinary Na/K ratio (P ≤ 0.048 for home SBP).

CONCLUSION

These findings suggest that urinary Na/K ratio might be more strongly associated with home BP than with 24-h and daytime BP but was not associated with night-time BP.

Urinary sodium/potassium ratio as a screening tool for hyperaldosteronism in men with hypertension

Among individuals with hypertension, the prevalence of secondary hypertension has been reported to be ≈10%. More than half of individuals with secondary hypertension have associated hyperaldosteronism. However, given the current clinical environment, these patients often remain undiagnosed. We hypothesized that the urinary sodium/potassium ratio (Na/K) could be used as a simple, low-cost method of screening for hyperaldosteronism among individuals with hypertension in primary care and health examination settings. We recruited hypertensive individuals aged 30-69 years old who were not taking any antihypertensive medications from among participants in health examinations. Urinary Na and K were measured using second morning urine samples, and the plasma aldosterone concentration (PAC) was also measured. We evaluated the association of the second morning urine Na/K ratio (SMU Na/K) with a high PAC, defined as ≥90th percentile (24.3 ng/dL), using receiver operating characteristic (ROC) curves. Overall, 160 participants (108 men and 52 women) with a mean age of 54.3 years were eligible for this study. The area under the ROC curve for the relationship between SMU Na/K and high PAC was 0.77 (95% confidence interval [CI]: 0.59-0.95) in men and 0.64 (95% CI: 0.36-0.93) in women. In men, SMU Na/K values <1.0 could detect hyperaldosteronism with a sensitivity of 45.5%, a specificity of 97.9%, a positive predictive value of 71.4%, and a negative predictive value of 94.1%. The use of the urinary Na/K ratio may be appropriate as a method of screening for hyperaldosteronism in hypertensive men.

Parental educational status independently predicts the risk of prevalent hypertension in young adults

Identification of individuals at risk of hypertension development based on socio-economic status have been inconclusive, due to variable definitions of low socio-economic status. We investigated whether educational status of individuals or their parents predicts prevalent hypertension in young adult population, by analyzing data of more than 37,000 non-institutionalized subjects from Korea National Health and Nutrition Examination Survey 2008 to 2017. Although low educational status of individual subjects was robustly associated with elevation of systolic blood pressure and increased prevalence of hypertension in general population, its impact on prevalent hypertension differed across age subgroups, and was remarkably attenuated in young adults. Parental educational status was significantly associated with prevalent hypertension in young adults, but not or only marginally in elderly population. Low parental educational status was also associated with high sodium intake in young adults, irrespective of subject’s own educational status. These collectively indicate that parental educational status, rather than individual’s own educational status, better and independently predicts prevalent hypertension in young adults, and that young adults with low parental educational status are prone to intake more sodium, possibly contributing to the increased risk of hypertension development. We expect that our findings could help define young individuals at risk of high sodium intake and hypertension.

Household income and the risk of incident hypertension in employees at multiple workplaces in Japan: J-HOPE

This cohort study aimed to investigate the association between household income and incident hypertension in a Japanese employed population. During 2012, a total of 4314 normotensive daytime employees (3153 men and 1161 women) were included in this study. Participants had a wide range of occupations and were employed at one of 12 workplaces from various economic sectors in Japan. After a 2-year follow-up, incident hypertension was compared among groups according to household income: <5.0, 5.0-7.9, 8.0-9.9, and ≥10.0 million Japanese yen (¥)/year. A Cox proportional hazard model was used to calculate the hazard ratio for incident hypertension in each household income group, compared with the group earning <5.0 million ¥/year. The hazard ratios for men were 1.52 (95% confidence interval, 1.08-2.18) for 5.0-7.9 million ¥/year, 1.49 (0.98-2.27) for 8.0-9.9 million ¥/year, and 1.92 (1.23-3.01) for ≥10.0 million ¥/year after adjusting for age, baseline systolic blood pressure, worksite, type of occupation, number of family members, and smoking status. This positive relationship was attenuated but remained significant after further adjustment for alcohol consumption and body mass index, both of which were higher among men with higher household income. Conversely, there was no significant difference for women in the risk of incident hypertension among household income groups, although those with higher household income tended to have a lower risk of incident hypertension. Household income is positively associated with the onset of hypertension in Japanese employed men working daytime hours.

Sodium/potassium ratio change was associated with blood pressure change: possibility of population approach for sodium/potassium ratio reduction in health checkup

Recently, the sodium (Na)/potassium (K) ratio was reported to be associated with blood pressure (BP). A Na/K ratio self-monitoring device using spot urine was established recently. Here, we assessed whether the urinary Na/K ratio change measured using the Na/K device was associated with BP change in a health checkup setting. We targeted 12,890 participants who attended the health checkup in Tome City, Miyagi between 2017 and 2018. Tome City introduced urinary Na/K ratio measurements during health checkups since 2017. For each year, we compared the baseline characteristics according to the urinary Na/K ratio and BP level. We assessed the relationship between change in urinary Na/K ratio and BP change using multiple regression analyses adjusted for age, sex, and change in body mass index (BMI) and alcohol intake. The average urinary Na/K ratio was significantly lower in 2018 than in 2017 (5.4 ± 3.0 to 4.9 ± 2.2, P < 0.01). The systolic BP of the participants in 2018 (130.9 ± 17.4 mmHg) was lower than that in 2017 (132.1 ± 17.9 mmHg). Moreover, the change in systolic BP and diastolic BP was positively associated with the change in urinary Na/K ratio. In conclusion, the association of the change in urinary Na/K ratio with hypertension and changes in systolic and diastolic BP can be explained by a change in alcohol intake, BMI, and urinary Na/K ratio. Therefore, measuring the urinary Na/K ratio in community settings is a potential population approach for counteracting hypertension.

Perspectives of patients and physicians regarding hypertensive management from an online survey for excellence: a subanalysis of the PARADOX study by physician categories

An existing clinical problem in Japan is the high prevalence of uncontrolled hypertension despite the availability of various effective therapies. Here, we analyzed survey data to gain insight into this paradox from physicians’ perspectives, with results categorized according to specialty (i.e., with or without certification by the Japanese Society of Hypertension [JSH]), institution type, gender, and age. A web-based survey of typical educational activities for patients regarding hypertension management was conducted in Japan between October 19 and 31, 2017. Differences between physician groups were investigated per category. Survey results from 541 physicians were analyzed: 59 JSH certified (i.e., ‘specialist’) vs 482 non-JSH certified (i.e., ‘nonspecialist’) physicians; 192 general practitioners vs 349 hospital physicians; 500 males vs 41 females; and 178 younger (mean age: 40.7 years), 174 middle-aged (52.0 years) or 189 older (61.3 years) physicians. The most statistically significant differences between groups were observed in the category of physician specialty. Compared with nonspecialists, specialist physicians were more conscious of providing education on patient lifestyle modifications, more aware of patient- and physician-derived issues, and understood and followed the treatment guidelines. General practitioners cared more about the patient’s burden than did hospital physicians. Younger physicians identified the need to incorporate the patient’s perspective into their treatment. This analysis shows that the provision and perceptions of education differ between physician categories. Compared with specialist physicians, nonspecialists were less likely to provide adequate guidance on lifestyle modifications, possibly due to their uncertainty in understanding treatment guideline recommendations. Further education of nonspecialists on hypertension management may be warranted.