Impacting incidence of disease through population‐based interventions: Appraisal of theARICstudy findings

Chronic kidney disease (CKD) is a global health burden with a high economic cost to health systems. The prevalence of CKD is increasing over time with an estimated global prevalence of between 11% and 13%.1 This trend is in part due to the aging population but is also associated with increases in hypertension (HTN) and diabetes mellitus. Very early researchers such as Richard Bright (1827) and Ludwig Traube (1856) associated “increased arterial pulse tension” with hypertensive cardiac and renal sequelae, such as “dropsy” and “nephritis.”2 This increase in HTN prevalence seems to be a particularly prominent factor affecting the CKD epidemic as the number of patients considered to be hypertensive has increased exponentially over the past decades.3 A study performed between 1907 and 1919 in ≥ 140 000 healthy adults applying for life insurance in the New York region suggested that a blood pressure of 140 (systolic)/90 (diastolic) mm Hg was abnormal because it reflected only 5%-6% of the population in the United States.4 Conversely, using this same cutoff it is currently estimated that 32% of the American population has HTN and 46% if the new cutoff of 130/80 in the 2017 guidelines is applied, leading to approximately a 7-fold increase in the population of hypertensive individuals over the past century.5 By postulating that the increase in CKD prevalence is directly related to the increase in HTN prevalence, one would think that any intervention at a population level to target the first would lead to a decrease in the second. The Atherosclerosis Risk in Communities (ARIC) study is a prospective study following a population-based cohort of 15 792 adults aged 45-64 years at study visit 1(1987-1989) from 4 US communities (Forsyth County, NC; Jackson, MS; suburbs of Minneapolis, MN; and Washington County, MD). It was designed to investigate the etiology of atherosclerosis and its clinical sequelae and variation in cardiovascular risk factors, by race, sex, and place over time.6 Participants attended subsequent visits at 3-year intervals until their fourth visit (1996-1998). Visit 5 occurred during 2011 to 2013.7 Physical examinations and standardized questionnaires were administered at each visit. Predicted benefits from blood pressure reductions were estimated and showed that a modest population-wide 1 mm Hg decrement in systolic blood pressure (SBP) was associated with an estimated 11.7 and 13.4 fewer CKD events per 100 000 person-years (PY) in African Americans and white Americans, respectively. This study illustrates elegantly how simple lifestyle modifications could lead to regression of disease endemic. According to the investigators’ estimates, it could potentially prevent around 10 000 CKD events per 100 000 PY if applied nationwide. Lifestyle interventions to decrease BP were highly emphasized in the latest guidelines as a cornerstone of high BP lowering strategies, taking preeminence over drugs at earlier stages of hypertension.5 Indeed, besides population aging, current lifestyle trends can indeed easily account for the growing epidemics of HTN and CKD and if modified could possibly reverse the current trend. They include physical activity, sodium intake, potassium intake, weight, smoking, and alcohol intake. The inverse relationship between physical activity and level of BP and hypertension has been well demonstrated in a number of epidemiological studies8 and the beneficial effect of regular endurance exercise training on blood pressure and quality of life in patients with hypertension has been well studied.9 At the beginning of the 20th century, before the generalized use of cars and modern public transportation, the level of daily physical activity was likely higher for the general population than now, possibly accounting to a certain extent for the lesser prevalence of HTN and CKD then. Moreover, habitual moderate exercise, independently of its effect on BP, may decrease the incidence of CKD in middle-aged and older men.10 Reducing sodium intake and increasing potassium intake are also approaches advocated to decrease both BP and incidence of CKD. Populations shown to have low sodium intakes (< 100 mmol/24 h) are typically remote economically undeveloped communities, whereas those shown to have higher sodium intakes are generally urban economically developed communities,11 the latter model replacing progressively the former one in today’s industrialized societies and accounting possibly as well for the increased hypertension and CKD prevalence. The positive association of sodium with blood pressure has been confirmed in a number of studies, whether clinical trials of sodium reduction and blood pressure (both randomized12 and nonrandomized13), or population observational studies.14 However, it is worth noting that reduction of sodium as a population-based approach for CKD prevention has had mixed results despite being advocated in many guidelines.15 In addition, both high and low sodium intakes were recently associated with incident chronic kidney disease in patients with normal renal function and hypertension in a Korean community-based cohort.16 Conversely, in 13 917 participants from the National Health and Nutrition Examination Survey (NHANES) where sodium and potassium intake were calculated from 24-hour recall and evaluated in quartiles, higher intake of sodium and potassium were associated with lower odds of CKD among US adults.17 However, in a population-based cohort of Dutch men and women aged 28-75 years, low potassium excretion reflecting low intake but not high sodium excretion was associated with increased risk of developing chronic kidney disease.18 In summary, although the optimal sodium intake remains uncertain, increasing potassium intake seems to be an effective strategy to decrease both BP and CKD incidence. Regarding smoking, it seems to be an independent risk factor for both HTN and CKD.19 Central SBP and pulse pressure are higher in smokers than in nonsmokers20 and cigarette smoking increases the daytime and average 24-hour BP and heart rate.21 In addition, smoking cessation is associated with lower BP increment and minor HTN risk, independently of potential confounders.22 Moreover, in a Japanese population, continuing smokers showed a 2-fold or higher risk of developing proteinuria whereas discontinuation of smoking substantially reduced the risk.23 In summary, as HTN and CKD seem to have common risk factors, the recent findings of the ARIC study stress the importance of shifting the goals of care from affecting chronic disease progression to preventing chronic disease incidence through population-based interventions. None.