Effects of dietary instruction and sodium excretion feedback in hypertension clinic patients

Effects of dietary instruction and sodium excretion feedback in hypertension clinic patients
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  BEHAVIOR THERAPY 26, 721-732, 1995 Effects of Dietary Instruction and Sodium Excretion Feedback in Hypertension linic Patients PATRICIA M. DUBBERT WILLIAM C. CUSHMAN Jackson Department of Veterans ffatrs Medical Center Umverstty of Mtsslsslppl School of Medtcme EDWARD F MEYDRECH Umverstty of Mtsslsstppl School of Medicine ABBY K. ROWLAND PATRICIA MAURY Jackson Department of Veterans ffairs Medical Center Black and White patients from a VA Medical Center hypertension cllmc serving a rural, elderly populaUon were randomly assigned to one of three interventions : a) one session of individualized instruction for 87 mmol/day reduced sodmm diet; b) one session of 87 mmol/day reduced sodmm diet instruction plus a means of estimating urine electrolyte excreuon at home; or c) instructions to maintain the usual d~et until reevaluated (control). At 3-month follow-up, reduction m 24-hour urine sodium ex- cretion was s~gnificantly greater in participants rece~wng d~etary instructions w~th feed- back than m controls. White paruc~pants w~th access to feedback had the greatest reduc- tion m urine sodium Results support the feasibility of slgmficant sodium reduction m hypertensive patients foUowmg a single intervention session. Although the relationship between high levels of dietary sodium (Na) in- take and hypertension is still not fully understood (Muntzel Drueke, 1992), clinical trials have demonstrated that therapeutic reductions in blood pres- sure can be achieved when dietary Na is reduced Cutler, Follman, Elliott, This research was supported by Department of Veterans Affairs Merit Review funding to Dr Dubbert. The authors acknowledge apprecmtion for consultation m the design and implementa- tion of the study from Herbert Langford, M.D. (deceased) We also thank Lisa Terre, Ph.D. and Mary Vavra L~ggett for their assistance w~th data collection. Dr. Cushman is now at the Memphis Department of Veterans Affairs Me cal Center and Univer- sity of Tennessee College of Me cme. Address correspondence to: Patncla M Dubbert, Ph D, Psychology (116B), VA Medical Center, Jackson, MS 39211 Phone 601-364-1350, Fax 601-364-1390. 721 0005-7894/95/0721-073251 0/0 Copyright 1995 by Association for Advancement of Behavtor Therapy All rights of reproduction in any form reserved  722 DUBBERT ET AL Suh, 1991; Elmer, Grimm, Flack, Laing, 1991). The Fifth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (Joint National Committee, 1993) recommended moderate Na intake reduction to 100 millimoles (2,300 milligrams) or less per day as an intervention for primary prevention and treatment of established hyperten- sion. This recommendation was made to acknowledge the evidence that blood pressure response to Na restriction is variable, with Blacks, the elderly, and individuals with elevated blood pressure most likely to show salt sensitivity (Joint National Committee 1993). At present, the only practical means of evalu- ating the effect of a restricted Na intake for a given individual is a dietary trial (Pecker Laragh, 1991). Despite the potential benefits of Na moderation, experience with poor ad- herence has led some investigators to conclude that it is not a useful interven- tion for many clinic patients (Muntzel Drueke, 1992). The wide distribution of Na in processed and convenience foods, increasing frequency of dining out, and the difficulty of assessing success in Na reduction are important obstacles to dietary Na moderation (Elmer, Grimm, Flack, Laing, 1991; Kumanyika, 1991). Although individual adherence to weight loss interventions can be in- directly assessed by simply weighing the individual on an accurate scale, ac- curate measurement of change in Na intake requires repeated assessment of urine collected over a 24-hour period (Weinberger, 1989). In an attempt to develop simpler methods of monitoring adherence, researchers have taken ad- vantage of the close relationship between Na and chloride (C1) in Western diets and have demonstrated the feasibility of using overnight urine collections as a means of estimating 24-hour excretion (Jeffery, Mullenbach, Bjornson- Benson, Prineas, Forster, 1987; Kaplan et al., 1982; Luft, Sloan, Fineberg, Free, 1983). Researchers have also explored methods of using the Na and/or C1 content of overnight or 24-hr urine collections to enhance adherence by providing feed- back to patients attempting to reduce Na in their diets (Cohen et al., 199l; Luft et al., 1984). Although promising in concept, the value of feedback has never been clearly demonstrated in Na moderation interventions with hyper- tension patients. One well-controlled study found no effect (Cohen et al.), and in two studies that found a beneficial effect, the feedback was confounded with such potentially critical components as diet instruction (Kaplan et al., 1982) and social support and group problem-solving (Nugent, Carnahan, Sheehan, Myers, 1984). Although hypertension is a major health problem for Black Americans, only one of the previous studies of Na feedback (Kaplan et al.) included more than a small proportion of Blacks. There remains a need to demonstrate that lifestyle changes such as dietary Na moderation can be achieved in a cost-efficient manner and with a broad spectrum of populations at risk. The present study, therefore, was designed to evaluate the effects of a single dietary instruction session, with and without a means of obtaining feedback about Na excretion, at the initiation of Na moderation intervention. Participants were drawn from a clinic serving pri- marily an aging rural population of elderly men with low levels of income. We hypothesized that Black and White patients given dietary instructions would reduce Na excretion significantly more than patients told to maintain their  SODIUM FEEDBACK 7 3 usual diets and that patients given access to feedback would show greater reduc- tions in urine Na than those given instructions without feedback. The study was not designed to evaluate the effects of reduced Na intake on blood pressure. ethod Partictpants Participants were 122 patients enrolled in a VA Medical Center hyperten- sion clinic serving about 1,000 eligible veterans from a large portion of Mis- sissippi and part of eastern Louisiana. Patients eligible for the study had a diagnosis of essential hypertension, a stable diastolic blood pressure such that they were not expected to need a change in medications for 3 months and urine Na excretion 1> 100 millimoles (mmol)/24 hours. Patients requiring im- mediate dietary intervention for diabetes or other conditions, or who were judged by their primary care provider to be unlikely to beqefit from the di- etary intervention due to current alcohol abuse, psychosis, or organic brain disease, were excluded. Patients involved in trials of investigational antihyper- tensive drugs were also excluded. Participants received no remuneration or travel expenses for their participation in this study. Recruitment and Randomization About 250 potential participants were referred by the nurse practitioner or physician s assistant most familiar with their care. Potential participants met briefly with the study dietitian at the conclusion of their hypertension clinic visit to assess their willingness to consider dietary change. To avoid reactive changes prior to randomization, potential participants were not told the na- ture of the changes which would be required. The approximately 200 patients who expressed interest were scheduled for a baseline visit; 186 reported for the screening visit with a 24-hr urine collocation as instructed. On the day of the baseline visit, the study technician screened potential par- ticipants urine specimens while they completed their regularly scheduled hyper- tension clinic visits. The 158 who met the study entry criteria were then seen by the research dietitian, who explained the study and obtained informed con- sent using documents approved by the appropriate committees for the protec- tion of human subjects. After providing demographic information, a diet his- tory and 24-hr diet recall, participants were randomized into one of the three groups using a random numbers table. (After about half the participants had been entered into the study, baseline characteristics of the three groups were examined to insure that the randomization process was producing equivalent groups. We found that two of the groups were markedly unbalanced with re- spect to race. Thereafter, we stratified randomization by race and overrecruited Blacks to one group and overrecruited Whites to another in order to improve the racial balance.) Data ollection The primary dependent measure was 24-hr urine Na excretion, used as an indirect estimate of Na intake. Participants were given collection bottles and received a set of written instructions regarding collection of 24-hr urine samples.  7 4 DUBBERT ET AL Participants with telephones also received a phone call a day or two in ad- vance to remind them when to begin their urine collections. At baseline, they were instructed to divide the urine collection into day and night portions. In addition to Na content, urine collections were analyzed by the medical center laboratory for potassium K) and creatinine excretion. Although urine Na and K vary greatly within and between individuals depending on recent dietary intake, urine creatinine, which is related to body weight and muscle mass, re- mains relatively constant for an individual over time Weinberger, 1989). Col- lections with total creatinine less than 0.6 g or greater than 3.6 g were excluded from analyses because they are considered as likely to represent less than or more than a 24-hr collection, respectively, Blaufox et al., 1992). Change in urine Na : creatinine was also calculated; this measure was used in a previous Na feedback study to help control for error due to inaccurate timing of urine collections Kaplan et al., 1982). Demographic and health history information were obtained by interview and medical record review. Sitting blood pressure BP) values obtained during the immediately preceding hypertension clinic visit were recorded at each of the two research visits, and body weight was also assessed. A brief semistruc- tured diet behavior interview was conducted at the 3-month follow-up visit with participants randomized to the two diet intervention groups. This inter- view utilized open ended questions to elicit information about support received from the primary food preparer and types of behavior changes participants attempted to reach their Na moderation goal. Responses were coded by a re- search assistant unfamiliar with the study participants or other outcome data. Treatment Interventton Condmons 1) Dtet Instructton with Feedback DI/FB). Participants randomized to the DI/FB group received one individualized dietary instruction with the Na in- take goal set at 87 mmol 2000 mg) per day. These instructions required about 1 hour for each participant and included simple take-home educational materials developed by the research dietitian which were adapted to local cooking styles and food preferences. Because of the extremely limited waiting space for the clinic at the time the study was conducted, patients were dis- couraged from bringing family members with them, and therefore, participants were given instructions in the absence of their spouse or other primary food preparer. The dietitian strongly encouraged participants to give the educa- tional materials on diet to their primary food preparer. In addition to the dietary instructions, DI/FB participants were given feed- back about recent levels of Na intake estimated from the C1 content of the night portion of the urine collections they had brought with them. C1 in the urine was measured by the research technician using CI titrator sticks Quantabs, Fisher Scientific), which have been suggested by previous investigators as a means to estimate Na intake and document compliance to dietary Na restric- tion Jeffery et al., 1987; Luft et al., 1983). The dietitian spent about 10 additional minutes with DI/FB participants providing verbal and written instructions about how to use the Quantabs to estimate adherence to the goal level of Na intake. They were shown the range on the Quantab strip that would correspond to the Na excretion goal, and  SODIUM FEEDBACK 7 5 how this compared with the results from the night specimen they had brought in the day of instruction. Participants were told this method was simple but not very accurate compared with hospital laboratory procedures; therefore they were asked to test their overnight urine three times a week (on Monday, Wednesday, and Friday mornings) and judge their success in reducing Na in- take by the overall pattern rather than any one day's results. They were given supplies sufficient for 12 weeks. To encourage adherence and allow the study team to monitor progress, the participants were also given stamped, addressed envelopes to return the Quantabs each week. 2) Diet Instruction DI). Participants assigned to the DI group received the same type of individualized dietary instruction given DI/FB participants with the Na intake goal set at 87 mmol (2000 rag) per day. Like DI/FB participants, they were seen without the primary food preparer. They were given no feed- back about the results of the urine Na or Cl measures. 3) Control C). After completing the assessment, the C group participants were told not to make any changes in their usual diet unit reevaluated at their next visit. At the 3-month visit, they were referred to the outpatient dietitian for appropriate diet instructions. Follow Up All participants were scheduled for their next hypertension clinic appoint- ment 3 months following the baseline study visit, and their 3-month research follow-up visit was scheduled for the same day. esults Participant Screening and Drop-Out Of the 186 patients screened for the study, 28 were excluded from randomi- zation because baseline urine Na was < 100 mmol/d and/or creatinine was outside the accepted range. Thirty-one of the 158 randomized failed to return for any followup visits, and 4 of those who did return brought incomplete urine collections. One additional participant had to be excluded due to loss of covariate data. The 36 patients without postintervention data included 21 Blacks and 15 Whites; 11 were from DI/FB, 13 from DI, and 12 from the C group. The dropout by race was not significant, X 2 (1) = .603, p = .44. Ex- amination of baseline measures revealed no significant differences between those who completed 3-month follow-up and those who dropped out. Participant Character~sttcs Table 1 shows the characteristics of participants completing the study. Overall, racial composition and age distribution of the sample approximated the distribution in the clinic from which participants were recruited. After dropouts were excluded, the final proportion of Black participants within in- tervention groups was: DI/FB = 49 ; DI = 57 ; and C = 61 . Demo- graphic characteristics were similar across races and groups. Most (76 of White and 74°70 of Black) participants were married; few (20 of Whites and
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