(RxWiki News) Heart disease is the leading cause of death and disability around the world, and most cases are due to diet and lifestyle factors. But which factors matter the most?
A recent study found that the average blood pressure and rates of death from stroke and heart disease in English adults decreased significantly between 2003 and 2011.
The researchers believe that these drops were closely related to the significant reduction of daily salt intake during the same period.
These researchers suggested that greater efforts at reducing the average daily salt intake of adults are needed to prevent more deaths due to stroke and heart disease.
"Discuss your daily salt intake with a doctor."
The lead author of this study was Feng J. He, MD, from the Wolfson Institute of Preventive Medicine of Barts and The London School of Medicine and Dentistry at Queen Mary University of London in London, United Kingdom.
The study included 31,672 adults who participated in the the Health Survey for England — a survey of a random sample of the English population — in 2003, 2006, 2008 and 2011.
All participants were 16 years old or older, with the average age being roughly 50 years old, and approximately 90 percent of the participants were white.
Each participant had their blood pressure measured when they were surveyed. Demographic data, smoking status and alcohol, fruit and vegetable consumption were also collected.
The researchers determined the national average salt intake based on measurements of 24-hour urinary sodium taken from participants of another survey — called the National Diet and Nutrition Survey — between 2000 and 2011.
Cases of death due to stroke and ischemic heart disease (IHD) were identified from the Office of National Statistics. IHD happens when the arteries around the heart start to narrow due to a buildup of plaque, making it difficult for blood to flow to and from the heart.
The findings showed that from 2003 to 2011, there was a 42 percent reduction in the stroke death rate and 40 percent reduction in the IHD death rate.
During the study period, the participants' average blood pressure decreased by 3.0/1.4 mm Hg, and their average salt intake decreased by 15 percent. Average cholesterol levels also dropped between 2003 and 2011.
A total of 19 percent of the participants smoked cigarettes in 2003, decreasing only 14 percent in 2011. In addition, the average vegetable consumption increased by 0.2 portions per day, and the average body mass index (height to weight ratio) increased by 0.5 kg/m2.
The researchers suggested that the decreases in stroke and IHD death rates were related to these changes in blood pressure, cholesterol level, salt intake and vegetable consumption, as well as the improvements in blood pressure, cholesterol and heart disease treatments during 2003 to 2011.
Among participants who were not taking any high blood pressure medications or any medications that might affect blood pressure, blood pressure dropped by an average of 2.7/1.1 mm Hg during the study period. This drop was independent of age, sex, ethnicity, education level, household income, alcohol consumption, fruit and vegetable consumption and body mass index.
Dr. He and team believe that this decrease in blood pressure among untreated blood pressure patients was more associated with the reduction of salt intake than high blood pressure medications.
"It's interesting that there are parallels in decreases in salt consumption and cardiovascular mortality during that same period of time. However, we're still not 100 percent sure exactly what the relationship is between salt intake, blood pressure, and mortality," said Jeffrey Schussler, MD, an interventional cardiologist at Baylor University Medical Center's Heart and Vascular Hospital in Dallas, TX.
"For my patients with either high blood pressure or fluid retention, I do recommend reducing salt intake in their diet," Dr. Schussler said.
The researchers noted a few limitations of their study. First, the researchers used nationally representative data from two different surveys. Second, potential affecting factors such as physical activity levels were not measured at each survey year. Third, the participants from the National Diet and Nutrition Survey were from multiple countries in the United Kingdom, whereas the rest of the data came from participants from England only.
This study was published on April 14 in BMJ Open.
Dr. He is a member of Consensus Action on Salt & Health (CASH) and World Action on Salt & Health (WASH) — both of which are non-profit charitable organizations. Dr. He does not receive financial support from either CASH or WASH.
Study co-author Graham A. MacGregor is also associated with CASH and WASH, and co-author Sonia Pombo-Rodrigues is an employee of CASH.