August 28, 2017
High daily salt intake is associated with a substantial increase in an individual's risk of developing heart failure, independent of other risk factors, suggests one of the largest studies to accurately measure salt consumption.
The analysis of more than 4500 individuals, presented here at the European Society of Cardiology (ESC) 2017 Congress, indicated that individuals who consumed more than 13.7 g of salt per day had an almost doubling of the risk of developing heart failure compared with those who consumed less than 6.8 g per day.
In a press conference featuring the study, lead researcher Dr Pekka Jousilahti (National Institute for Health and Welfare, Helsinki, Finland) said that there is now enough evidence to start taking action to reduce salt intake both in Europe and globally.
To those ends, he called for legislation and education to help tackle the issue, alongside collaboration with the food industry.
Asked by theheart.org | Medscape Cardiology how easy it will be for individuals to reduce their salt consumption, given that food manufacturers add salt to their products, Jousilahti said that is one of the first things to address, given that "about 80% of salt intake is in processed foods."
Taking up the question, press conference cochair Joep Perk (Oskarshamn District Hospital, Sweden) pointed out that "the Finns have been very successful in legislating" to reduce the salt consumption of their population, which has been accompanied by a drop in stroke rates.
Jousilahti confirmed that, during the 1970s, average daily salt consumption in Finland was approximately 14 g per person, but now it's about 6 g for females and 7 g for males. "Of course, we still have not got to the recommendations, but it has been a nice downward trend," he said.
Commenting on the findings for theheart.org | Medscape Cardiology after the press conference, Dr Ignacio Ferreira-Gonzalez (University Hospital Vall d'Hebron, Barcelona, Spain), who was not involved in the study, pointed out that it is very difficult to measure salt consumption.
Therefore, for him, one of the strengths of the study is that, by determining urine sodium-excretion levels, they measured salt consumption "in a very accurate way."
He nevertheless agreed with Jousilahti that it will be a challenge to reduce salt consumption due to the salt added to foods by manufacturers, although "maybe it's not so difficult in the southern countries of Europe, because we have not become as used to processed meals as in the north."
Presenting the study, Jousilahti pointed out that, while the biological need for salt is estimated at just 2 to 3 g per day and the World Health Organization recommends a maximum intake of 5 g of salt per day, salt consumption is higher than both of those figures in most populations.
High sodium chloride intake is a major cause of hypertension and a known risk factor for coronary heart disease and stroke. However, the degree to which high salt intake increases the risk of heart failure has not been determined.
As the gold-standard technique is to determine average sodium excretion from 24-hour urine samples, however, there have been few population-based cohort studies that have accurately assessed the impact of salt consumption on heart-failure risk.
To investigate further, the team studied 4630 men and women aged 25 to 64 years who took part in the North Karelia Salt Study or the National FINRISK Study between 1979 and 2002.
Baseline clinical measurements, blood samples, and 24-hour urine samples were collected, with 1 g of salt intake equated to 17.1 mmol of sodium excretion. In addition, the participants completed health-behavior questionnaires.
National health records were then examined to determine the rate of incident heart failure over a mean 12-year follow-up, based on causes of death, hospital discharge summaries, and drug reimbursements.
There were a total of 121 cases of incident heart failure during follow-up.
Cox proportional hazard models by quintiles of salt intake, adjusted for age and sex, revealed that, compared with a daily salt intake of <6.77 g/day, an intake of 6.77 to 8.80 g/day was associated with a hazard ratio for a new heart-failure diagnosis of 0.83.
For a daily salt consumption of 8.81 to 10.95 g/day, the hazard ratio for incident heart failure was 1.40, while the hazard ratio for a daily consumption of 10.96 to 13.73 g/day was 1.70, and that for daily consumption >13.73 g/day was 2.10 (P=0.002 for trend).
Hazard Ratios for Incident Heart Failure
|Salt intake (quintiles)||Fully adjusted hazard ratio|
|<6.77 g/day||1.0 (reference)|
|P for trend||0.009|
Jousilahti noted that, due to potential regression-dilution bias resulting from the single baseline estimate of salt intake, it is likely that the observed risks underestimate the true risk posed by increased salt intake and that the optimal salt intake is likely to be less than 6.77 g/day.
He said that to offer a more detailed estimate of the heart-failure risk, larger studies of pooled population cohorts are required.
During the discussion following the presentation, an audience member asked whether the association between salt intake and heart-failure risk could be confounded by the known association between salt intake and hypertension, as the researchers defined new heart failure based on drug prescriptions.
She asked: "To what extent could you differentiate drugs that were prescribed for hypertension and not for heart failure?"
Jousilahti said that validation studies have previously been conducted on the data set to verify that it is possible to distinguish between the two conditions, although he agreed that it is "one of the risks" when conducting studies such as these.
Session cochair Dr Maryam Kavousi (Erasmus Medical Center, Rotterdam, the Netherlands) then asked whether the research team could control further for this relationship by restricting the analysis to those who developed hypertension prior to the diagnosis of heart failure.
Jousilahti replied that he and his colleagues could do such an analysis, adding: "We have not published that study yet, but maybe that's a good suggestion to do it."
The authors declare no relevant financial relationships.