Effects Of Reduced Sodium Intake On Hypertension Control In The Elderly - Brief Article

Nutrition Research Newsletter, April, 2001

Hypertension and its treatment with medication are extremely common in the elderly. In certain subgroups, hypertension is nearly ubiquitous. For example, the prevalence of hypertension among African-American women aged 60 to 69 years is 78%. Medication used is also highly prevalent in the elderly, ranging from 31% of Mexican-American women with hypertension 70 years and older, to 70% of African-American women with hypertension 70 years and older. Sodium restriction is widely advocated as a means to reduce BP and control hypertension in older persons, yet evidence is sparse to support the effects of a reduced sodium intake on BP and hypertension control in this population. The Trial of Nonpharmacologic Interventions in the Elderly (TONE) was a randomized trial that tested weather reduced sodium intake and/or weight loss can maintain satisfactory medication-treated hypertension control in older persons with hypertension. In brief, TONE demonstrated that a reduced sodium intake and weight loss, alone or combined, could effectively control hypertension. The objectives of the present study, which focuses only on the sodium component of TONE, were to examine the effects of a reduced sodium intake in subgroups defined by sex. In addition, the researchers examined dose-response relationships and the effects of a reduced sodium intake on dietary intake of other nutrients, and the occurrence of adverse events.

The study population consisted of healthy persons (aged 60-80 years) with systolic BP of less than 145 mm Hg and diastolic BP of less than 85 mm Hg, while taking 1 anti-hypertensive medication. Individuals provided a medical history, underwent a physical examination, and had routine laboratory tests to confirm eligibility. The median duration of follow-up was 29 months (maximum of 36 months). Twenty-four-hour urine collections were obtained twice prior to randomization and once at the 9-, 18-, and 30-month follow-up visits and at closeout. Twenty-four-hour dietary recalls were obtained twice prior to randomization and again at the 9- and 12-month follow-up visits and every 6 months thereafter. Overweight participants were randomly assigned to one of the four following groups: (1) combined weight loss and reduced sodium, (2) reduced sodium alone, (3) weight loss alone, (4) usual lifestyle (UL) control group. Normal weight participants were randomly assigned to reduced sodium alone or UL groups. This article presents data on both overweight and normal-weight subjects that were assigned to the reduced sodium alone, or UL groups.

Intervention groups were formed, consisting of 9 to 12 participants, and met weekly during a 4-month "intensive" phase, and then a 3-month "extended" phase with biweekly meetings, and a maintenance phase. Participants were asked to modify only those aspects of their diet that led to high sodium intake. The goal for reduced sodium groups was to achieve and maintain a 24-hour dietary sodium intake of 80 mmol/L or less of sodium, as measured by 24-hour urine collections. During the intervention sessions, participants learned about sources of sodium and how to adapt the reduced sodium lifestyle recommendations to their own individual situations. Meetings for the UL group were held on a regular basis as well, and featured speakers who led discussions on topics unrelated to BP, cardiovascular disease, or nutrition.

Drug withdrawal began 90 days after the first group intervention session. As the medication was tapered, participants were evaluated weekly. Attendance at closeout visits was 90% and 93% in the reduced-sodium and UL groups. The reduced-sodium group achieved and maintained a substantial reduction in sodium levels. More than 40% of reduced-sodium participants had an absolute urinary sodium excretion of 80 [micro]M/d or less in contrast to less than 15% or UL participants. Overall, urinary sodium excretion was reduced by 40 [micro]M/d in the reduced-sodium group, net of UL. The reduced-sodium group experienced a mean reduction in systolic BP of 4.3 mm Hg and in diastolic BP of 2.0 mm Hg, net of BP change in UL. The occurrence of cardiovascular events was similar in the two groups, except for a tendency toward less angina in the reduced-sodium group compared with the UL group. Headache also occurred less frequently in the reduced-sodium group. Compared with the UL group, intake of total energy, dietary fat, saturated fat, mono-unsaturated fat, iron, calcium, thiamin, and riboflavin declined in the reduced-sodium group, while intake of potassium and magnesium increased.

Findings from this trial have important public health and clinical implications. Because hypertension is common in the elderly and because sodium reduction can substantially reduce BP, population-based and individualized efforts to reduce sodium intake are appropriate. The TONE trial provides convincing evidence that individualized counseling can reduce BP and control hypertension. Such evidence supports current efforts to expand Medicare coverage of nutrition services.