Hypertension, or high blood pressure, is a major risk factor for cardiovascular disease and contributes to nearly half of all cardiovascular disease–related deaths, including stroke, in the United States.1 Research suggests that even small reductions in sodium intake may lower blood pressure, help prevent the onset of hypertension, or help control blood pressure among hypertensive adults.2 The 2010 US Dietary Guidelines currently recommend limiting sodium intake to less than 2300 mg per day. Certain persons should limit their sodium intake to 1500 mg per day, including adults 51 years or older, African Americans, and persons with high blood pressure, diabetes, or chronic kidney disease.3
According to the Centers for Disease Control and Prevention, most sodium consumed comes from processed foods and foods prepared in restaurants, with more than 40% of sodium coming from the following 10 types of foods: breads and rolls, cold cuts and cured meats, pizza, fresh and processed poultry, soups, sandwiches, cheese, pasta dishes, meat-mixed dishes, and snacks such as chips, pretzels, and popcorn.4 Considering that foods prepared away from home comprise nearly half of all US consumer food expenditures,5 it is unsurprising that Americans consume on average 3300 mg of sodium per day, which is far more than current national recommendations.6
Current recommendations for state and local health departments to address high sodium intake at the state and local levels include the following: (1) increasing public awareness about the amount of sodium added to processed and packaged foods as well as the health outcomes of a high-sodium diet; and (2) encouraging vendors to reduce the amount of sodium in foods sold and purchased in cafeterias and vending machines in schools, worksites, and public institutions.6,7 In 2011, the Kansas Department of Health and Environment was awarded a cooperative agreement from the Centers for Disease Control and Prevention as part of the Sodium Reduction in Communities Program (SRCP) to implement community-based interventions to reduce sodium intake among Shawnee County, Kansas, residents over a 3-year period. As part of this initiative, the 2011 Sodium Reduction in Communities Shawnee County Survey, a multicomponent survey (which will henceforth be referred to as the “survey”) was conducted to collect baseline data on the prevalence of high blood pressure, sodium intake, and knowledge and behaviors related to sodium consumption among Shawnee County adults. The survey was designed to help guide program development and evaluation.
The prevalence of clinic-measured and self-reported hypertension and mean sodium intake among Shawnee County, Kansas, adults 18 years and older have been previously described.8 The purpose of the current study was to describe knowledge and behavioral indicators related to sodium consumption among this population.
The 2011 Sodium Reduction in Communities Shawnee County Survey was a population-based survey conducted during April-November 2011 and consisted of 3 components: telephone interview; clinic-measured height, weight, and blood pressure; and a Web-based Automated Self-administered 24-hour Dietary Recall (ASA24) interview.
The random digit–dial landline telephone interview component of the survey was conducted within the Kansas Department of Health and Environment and used the Kansas Behavioral Risk Factor Surveillance System (BRFSS) design.9 Survey questions were adapted from the BRFSS, the National Health and Nutrition Examination Survey (NHANES),10 the Kansas Cardiovascular Health Examination Survey,11 and other national and state surveys.
Participants who completed telephone interviews were then scheduled for an appointment to measure their height, weight, and blood pressure at the Shawnee County Health Agency facility in Topeka, Kansas. The NHANES anthropomorphic and blood pressure measurement protocols were used for this survey component.12,13 After measurement of height, weight, and blood pressure, participants, with assistance from project staff, completed the ASA24 interview at the health agency. The ASA24 is a Web-based interview tool created by the National Cancer Institute to estimate the calories and nutrient intake of an individual respondent over a 24-hour period.14 Participants were each provided a $25 gift card after completing all 3 survey components. The Kansas Department of Health and Environment Institutional Review Board approved the 2011 Sodium Reduction in Communities Shawnee County Survey prior to its implementation.
Clinic-measured hypertension was defined as an average systolic blood pressure of 140 mm Hg or more, an average diastolic blood pressure of 90 mm Hg or more, or the current use of blood pressure–lowering medication. Self-reported hypertension was defined as respondents who answered “Yes” to the survey question, “Have you ever been told by a doctor, nurse, or other health professional that you have high blood pressure?”
Mean sodium intake was calculated directly by the ASA24 statistical system and is based on the United States Department of Agriculture Food and Nutrient Database for Dietary Studies, which is a database of foods, their nutrient values, and their gram weights for typical food portions.
Table 1 describes selected telephone interview items and response options pertinent to this study. Demographics measured included age, sex, race/ethnicity, and highest level of education attained.
Data from all 3 components of the survey were combined and subsequently weighted using the iterative proportional fitting (“raking”) method to be representative of the population of Shawnee County adults living in private residences with landline telephone service. Two major steps were undertaken as part of the raking process. First, design weights were computed to reflect the disproportionate stratified sampling selection probabilities of households, as well as selection of one adult per household. Second, design weights were simultaneously adjusted along five dimensions: gender (male, female), ethnicity (Hispanic, non-Hispanic), race (white, black, other), age (18-24, 25-34, 35-44, 45-54, 55-64, 65-74, 75-84, 85+), and education (less than high school, high school or equivalent, some college, and college graduate). The weighted data analysis procedures were applied for computation of all statistics. Weighted prevalence and mean estimates were computed for hypertension status, sodium intake, and selected sodium knowledge and dietary behavior indicators. Rao-Scott χ2 tests and t tests were used to determine statistically significant between-group differences at the .05 significance level for weighted prevalence and mean estimates, respectively, across demographic subgroups including sex, age, annual household income, education level, and hypertension status. Because of relatively few nonwhite respondents, estimates were not computed across race/ethnicity subgroups. All data were analyzed using SAS software (version 9.3; SAS Institute Inc, Cary, North Carolina).
A total of 834 Shawnee County adults completed the telephone interview; of these, 695 (83%) attended clinic visits to complete the other 2 survey components. Weighted sample demographics are given in Table 2.
Hypertension status and mean sodium intake
Table 3 presents clinic-measured hypertension status and mean sodium intake among Shawnee County adults by selected demographic characteristics. Approximately one-third (34.3%; 95% confidence interval, 28.2-40.5) of adults had hypertension, based on clinical measures or current use of blood pressure–lowering medication. The prevalence of hypertension was significantly higher among adults 65 years and older than those aged 18 to 64 years (61.4% vs 28.2%, respectively; P < .0001), as well as among adults whose annual household income was less than $50 000 than those whose annual household income was $50 000 or greater (44.1% vs 25.0%, respectively; P = .004). There were no statistically significant differences in the prevalence of hypertension across sex groups or levels of educational attainment.
Mean sodium intake, based on ASA24 results, among Shawnee County adults was 3508 mg per day. Mean sodium intake was significantly higher among men than among women (4141 mg per day vs 2931 mg per day, respectively; P = .002), as well as among adults 18 to 64 years as compared with adults 65 years and older (3648 mg per day vs 2891 mg per day, respectively; P = .008) There were no statistically significant differences in mean sodium intake across annual household income groups, levels of educational attainment, or hypertension status.
Table 4 describes selected sodium knowledge and dietary behavior indicators as measured by telephone interview. Self-reported hypertension status and knowledge and behavioral indicators related to sodium consumption are based on results from participants who completed the telephone interview, regardless of their participation in subsequent survey components.
Food sources of sodium
Approximately 83.2% of adults strongly agreed or agreed that most of the sodium we eat comes from packaged, processed, store-bought, and restaurant foods, whereas 65.2% strongly agreed or agreed that only a small amount of the sodium we eat comes from salt added during cooking and from being added to food at the table.
Link between sodium intake and high blood pressure
Knowledge regarding the link between sodium intake and high blood pressure was very extensive among Shawnee County adults. Approximately 93.0% thought that a high-salt diet could cause high blood pressure, and a similar proportion (90.1%) strongly agreed or agreed that reducing the amount of dietary salt could reduce blood pressure.
There were no statistically significant differences in knowledge regarding food sources of sodium or the link between sodium intake and high blood pressure across sex groups, age groups, annual household income groups, levels of educational attainment, or hypertension status (data not shown).
Foods away from home
Adults ate 3.3 meals prepared outside the home per week, on average, and approximately 42.5% of adults ate more than 2 meals prepared outside the home per week. The percentage of adults who ate more than 2 meals prepared outside the home per week was significantly higher among men than among women (52.3% vs 33.7%, respectively; P < .001) and also among college graduates as compared with those with lower levels of educational attainment (55.0% vs 38.2%, respectively; P = .001). There were no statistically significant differences in the percentage of adults who ate more than 2 meals prepared outside the home per week across age groups, annual household income groups, or hypertension status.
Consumption of selected high-sodium foods
Nearly 1 in 10 adults (9.6%) ate salty snacks, and a similar proportion (8.5%) consumed processed meats, at least once per day in the past month. Relatively few adults ate frozen entrées (3.0%) or canned or packaged soup (2.3%) at least once per day in the past month. The percentage of adults who consumed salty snacks, processed meats, frozen entrées, or canned or packaged soup at least once per day in the past month did not differ statistically across sex groups, age groups, annual household income groups, levels of educational attainment, or hypertension status (data not shown).
Adding salt to foods
Nearly 1 in 4 adults (24.2%) added salt very often in cooking or preparing foods in their household. The percentage of adults who added salt very often in cooking or preparing foods in their household was significantly higher among those aged 18 to 64 years than those aged 65 years and older (26.0% vs 16.3%, respectively; P = .02), as well as among those who were not hypertensive as compared with those who were (28.9% vs 17.6%, respectively; P = .04). There were no statistically significant differences in the percentage of adults who added salt very often in cooking or preparing foods across sex groups, annual household income groups, or levels of educational attainment.
The prevalence of hypertension among Shawnee County adults is similar to national estimates; during 2003-2010, 30.4% of US adults had hypertension.15 Furthermore, self-reported hypertension status assessed through the telephone component of this survey was consistent with clinic-measured hypertension status, which validates the use of telephone-based surveys such as the Kansas BRFSS to assess this particular health indicator among adults. The average sodium intake among Shawnee County residents also parallels national data, which shows that Americans consume on average 3300 mg of sodium per day.6
Knowledge regarding food sources of sodium and the link between sodium intake and high blood pressure was extensive among Shawnee County adults. Furthermore, reported consumption of processed meats, salty snacks, frozen entrées, and canned or packaged soup was relatively infrequent. However, adults indicated eating slightly more than 3 meals prepared outside the home per week, on average, and 1 in 4 adults added salt very often in cooking or preparing meals. Unfortunately, despite extensive knowledge regarding food sources of sodium and the link between sodium intake and high blood pressure, mean sodium intake as measured by nutrient intake analysis among Shawnee County adults, including those with hypertension, exceeded current recommendations. This finding mirrors national data, which show that 95.0% of US adults aged 18 to 50 years with a sodium recommendation of less than 2300 mg per day consume 2300 mg per day or greater, while 99.4% of those with a sodium recommendation of 1500 mg per day consume more than 1500 mg per day.16
There are certain limitations to this study worth noting. Although survey results are generalizable to noninstitutionalized adults living in private households with landline telephone service, survey results do not apply to individuals without telephone service, those who reside on military bases or within institutions, or those who are unable to complete a telephone interview. However, these groups constitute a relatively small proportion of the Kansas population. In addition, unlike the 2011 Kansas BRFSS, which sampled adults living in households with landline phone service or cell phone–only service, data included in the current report are based only on sampled individuals living in households with a landline telephone. Because of insufficient cell sizes, data were not analyzed by race/ethnic status. In addition, estimates of mean sodium intake are based on a single 24-hour dietary recall per respondent. Ideally, estimates should be based on averages obtained from two 24-hour dietary recalls, which is the methodology used by the NHANES.17 Despite these limitations, the current study highlights a unique method for collecting data at the local level, which are typically lacking.
As previously discussed, excessive sodium consumption has significant public health implications for cardiovascular disease because of the reported association between sodium intake and high blood pressure.2 The Shawnee County SRCP is currently implementing practice-based public health interventions to increase public awareness of the health implications of excessive sodium intake and making environmental changes that support access to and availability of lower-sodium options in Shawnee County. For example, the SRCP Leadership Team is working with city and county government agencies, as well as private employers, to educate and support them in the voluntary adoption and implementation of procurement strategies that meet 2010 Dietary Guidelines for Americans for sodium consumption. Data from the current survey are being used to develop materials and educational presentations for organizations where procurement policies or other sodium-reduction strategies could potentially be implemented.
The Leadership Team is also partnering with 13 convenience stores in Shawnee County to increase access to and purchase of lower-sodium foods. Lower-sodium options are encouraged to consumers through the use of promotional displays with signage. In addition, a comprehensive mass media campaign has been developed to promote heart healthy, lower-sodium food choices using www.spotthesalt.com, social media, radio, TV, billboards, and print material throughout Shawnee County. Message design was based on results from focus groups with local citizens as well as data from the current survey.
Despite extensive knowledge regarding food sources of sodium and the link between sodium intake and high blood pressure, mean sodium intake among Shawnee County adults exceeds current recommendations. The Shawnee County SRCP is currently implementing interventions that support access to and availability of lower-sodium options in Shawnee County. The 2011 Sodium Reduction in Communities Shawnee County Survey highlights a unique method for collecting local-level data to inform and evaluate community-level sodium-reduction interventions. Although each of the SRCP strategies includes a detailed evaluation plan to monitor progress toward meeting short-term implementation objectives, a follow-up to the 2011 Sodium Reduction in Communities Shawnee County Survey in the future can provide valuable information regarding long-term impact at the county level.