In 2019, a total number of 1.72 million deaths and 40.54 million DALYs were caused by CVD due to dietary high sodium, respectively, increasing by 41.08% and 33.06% from 1990, which was mainly driven by population growth and population aging. The corresponding ASR of deaths and DALYs dropped by 35.1% and 35.2%, respectively, from 1990. The global CVD burden due to high sodium intake showed substantial disparities in genders, ages, WHO regions and SDI quintiles. The leading diseases caused by high dietary sodium were ischemic heart disease, stroke, and hypertensive heart disease. Expanding universal health coverage was highlighted to prevent and treat high dietary sodium related CVD burden worldwide.
A general decline of high dietary sodium related CVD burden was observed over the past decades, with the most pronounced decreases in high-income Asia-Pacific, Southeast Asia, Western and Central Europe. This indicates that global sodium reduction measures may have had a relatively good effect. In 2019, a total of 96 countries has been reported to have national salt reduction initiatives, with an additional 16 countries in their planning stages [2]. The main implementation strategies focus on interventions in settings, food reformulation, consumer education, front of-pack labeling, and salt taxation [17]. Continuous monitoring and reporting on progress of each intervention approach aids in determining whether these policies are effective, identifying gaps, and planning steps to achieve the targeted 30% reduction in salt intake.
Despite significant reductions in the ASR of deaths and DALYs, high sodium-related CVD burden remains a major public health challenge. Our results showed exposure to high sodium contributed to 1.72 million deaths and 40.54 million DALYs globally in 2019. The two major countries, India and China, where added salt is the primary source of dietary salt [18, 19], have the greatest CVD burden due to high sodium intake. It’s difficult to reduce salt intake in these countries due to the difficulty of changing dietary patterns. Evidence has shown salt substitutes lower blood pressure and major adverse cardiovascular events efficiently [20]. The main challenge in both countries now is how to make the necessary adaptations to ensure the strategy of salt substitutes effectively reduces salt intake, like overcoming the extra costs of salt substitutes, which are nearly double the price of standard salt. The Chinese central government has included salt reduction as one of the key components of China's health development agenda and set up the action group “Action on Salt China (ASC)” with the aim of achieving WHO’s recommended salt intake in China [19]. Notably, several Asian and African countries, including Pakistan, Nepal, Bangladesh, Ghana, Bhutan, faced an upward trend of high sodium intake-related CVD burden, which deserves more attention and support from United Nations (UN).
Numerous studies have shown that socioeconomic status has a measurable and significant effect on cardiovascular health [21, 22]. Residents in low-income areas were more likely to have insufficient awareness of the risk of excessive salt consumption and to have inadequate standards of care. Socioeconomic status also affects salt-induction strategies, which are more feasible in high and high-middle income countries. In 2019, a number of 52 high-income countries had national salt reduction initiatives in place, with interventions in food reformulation and front-of-pack labeling being typical strategic approaches. Meanwhile, 30 upper-middle and 13 lower-middle income countries had national salt reduction initiatives, with interventions primarily focused on food reformulation and consumer education [23]. Although the high salt diet-related CVD burden is the lowest in low SDI quintile, additional support is still warranted to develop policies and interventions to reduce excess salt intake in the low SDI regions, particularly those experiencing a nutrition transition towards greater intake of processed and packaged foods [24].
The CVD burden attributable to high sodium intake was heterogeneous across SDI regions in terms of demographic factors. The effect of population aging was noteworthy in the high SDI quintile but did not occur in the low SDI quintile. Such results likely reflect differences in demographic changes across SDI quintiles. Between 1990 and 2017, the proportion of people aged 65 years and older rose from 12.1% to 17.5% in high-income countries but dropped from 3.2% to 3.1% in low-income countries [15]. While population growth contributed significantly to the CDV burden in high-middle and middle SDI regions, population aging is predicted to be a major issue in these regions. National governments should weigh these variations when developing and implementing action plans in particular regions and countries.
Our findings suggested that women were relatively protected from high sodium intake related CVD, compared with men. This result was consistent with the Dietary Approaches to Stop Hypertension (DASH) diet study, in which the DASH diet with limited dietary sodium lowered more systolic blood pressure in women (10.5 mmHg) than in men (6.8 mmHg) [25]. Sex hormones as well as sex chromosomes undoubtedly play a role in the observed sex differences in cardiovascular disease [26]. In our analysis, the gap between males and females gradually decreased after 65-69 years old, the period after menopause, demonstrating this well. Additionally, differences in diet patterns and behaviors contribute to sexual dimorphic patterns. Females were found to have better diet quality and cognitive restraint than males [27]. This clinically meaningful sex difference necessitates rinsing awareness to implement sex-specific dietary salt control and to improve the prevention and treatment of its concomitant CVD in males.
The high dietary salt-related CVD burden is highly preventable, and timely intervention significantly improves outcomes. According to Song’s prediction model, a 4.3-year delay in finalizing sodium targets in the United States may cost over 250 000 lives by 2031 [28]. For now, the COVID-19 pandemic has not only stressed the healthcare systems, but also changed lifestyles due to social isolation, including an increase in consumption of unhealthy products [29]. It is vital for policy-makers to take actions to raise awareness of salt reduction among the public as well as to maximize industry compliance with the sodium-reduction targets as soon as possible. Our results indicated that UHC had a significant association with the CVD burden due to high salt intake among socioeconomic factors. However, at present, few countries specifically mention CVD care in their health benefits packages, and there is still limited information to guide policy around CVD and UHC [30]. Previous studies provided some cost-effective clinical services, which may serve as a starting point to improve the inclusion of CVD into UHC [31]. A call for future work from policy-makers to raise the profile of CVD on the UHC agenda to reach the target of a 25% reduction in NCDs by 2025.
Study limitations
This study has several limitations. First, the work reported here builds on the database of GBD 2019, which included only 92 sources from 53 countries of the high sodium intake exposure data and 21 sources from 6 countries of the high sodium intake attributable burden data [32]. Therefore, most countries' data was computed by the GBD method, so the reliability may be insufficient. Second, the effect of salt on cardiovascular outcomes was assessed indirectly, relying on the relationship between urine sodium, systolic blood pressure fluctuations, and cardiovascular outcomes, which inevitably raised data uncertainty. Third, the study is subject to all the general limitations described by the GBD collaboration [33]. For example, the sparse data in the low-SDI quintile may affect the accuracy of the estimates.