Wuopio J, et al. European Heart Journal Open 2023;3:2.

This study, published in the European Heart Journal Open, aims to investigate the relationship between salt intake and carotid and coronary atherosclerosis in a contemporary community-based cohort.

The authors used the Kawasaki formula to estimate 24-hour sodium excretion for participants at two Swedish Cardiopulmonary bioImage Study sites. This included a coronary computed tomography (n=9623), measurement of coronary artery calcium score (CACS, n=10289), and carotid ultrasound to detect carotid plaques (n=10700).

Results showed that increased sodium excretion was associated with an increased occurrence of carotid plaques, higher CACS, and coronary artery stenosis. The authors used ordered logistic regression and quintiles of est24hNa to calculate odds ratios.

This study found that increased sodium excretion was significantly associated with carotid atherosclerosis, atherosclerotic stenosis in coronary arteries, and overall coronary artery calcification, but only in minimal adjusted models. The association disappeared when adjusting for blood pressure and other risk factors, indicating confounding or other pathways for salt's harmful effects. Men had higher est24hNa, and the associations were only seen among men. No causal relationships could be established due to the observational, cross-sectional design of the study.

The study's strengths include a high number of participants with detailed characterization and state-of-the-art measurements of coronary atherosclerosis and carotid plaques. However, a limitation is the use of the Kawasaki formula to estimate 24-hour sodium excretion from spot urinary sodium samples, which has been criticized for creating biased results in previous studies. While the formula is good enough to estimate salt intake at a population level, it is not accurate enough to determine safe levels of salt intake on an individual level. Other limitations include unknown generalizability, residual confounding, and the observational, cross-sectional design of the study, which does not allow for causal relationships to be established.

Overall, the study found an association between est24hNa and cardiac and carotid atherosclerosis, primarily mediated by blood pressure but also influenced by other established risk factors.

When asked about the key takeaways of the study, investigator, Dr Jonas Wuopio said, "I believe doctors should emphasize the advice given by the World Health Organization or other medical societies to limit salt intake to about a teaspoon a day, and that this not just includes those patients with hypertension or known cardiovascular disease."