Estimating the effect of nutritional interventions using observational data: the American Heart Association's 2020 Dietary Goals and mortality

Abstract

Background: Because randomized trials of sustained dietary changes are sometimes impractical for long-term outcomes, the explicit emulation of a (hypothetical) target trial using observational data may be an important tool for nutritional epidemiology.

Objectives: We describe a methodological approach that aims to emulate a target trial of dietary interventions sustained over many years using data from observational cohort studies.

Methods: We estimated the 20-y risk of all-cause mortality under the sustained implementation of the food-based goals of the American Heart Association (AHA) 2020 using data from 3 prospective observational studies of US men [Health Professionals Follow-up Study (HPFS)] and women [Nurses' Health Study (NHS) and Nurses' Health Study II (NHS II)]. We applied the parametric g-formula to estimate the 20-y mortality risk under a dietary intervention and under no dietary intervention.

Results: There were 165,411 participants who met the eligibility criteria. The mean age at baseline was 57.4 y (range, 43-82 y) in the HPFS, 52.4 y (range, 39-66 y) in the NHS, and 40.2 y (range, 30-50 y) in the NHS II. During 20 y of follow-up, 13,241 participants died. The estimated 20-y mortality risks under a dietary intervention versus no intervention were 21.9% compared with 25.8%, respectively, in the HPFS (risk difference, -3.9%; 95% CI: -4.9% to -3.2%); 10.0% compared with 12.6%, respectively, in the NHS (risk difference, -2.6%; 95% CI: -3.1% to -1.8%); and 2.1% compared with 2.5%, respectively, in the NHS II (risk difference, -0.35%; 95% CI: -0.56% to -0.09%). The corresponding risk ratios were 0.85 (95% CI: 0.81-0.88) in the HPFS, 0.79 (95% CI: 0.75-0.85) in the NHS, and 0.86 (95% CI: 0.78-0.96) in the NHS II.

Conclusions: We estimated that adherence to the food-based AHA 2020 Dietary Goals starting in midlife may reduce the 20-y risk of mortality.

Keywords: American Heart Association 2020 Dietary Goals; g-formula; mortality; nutritional epidemiology; target trial.

FIGURE 1

Flowchart of eligible individuals for the emulation of a target trial of dietary interventions in the Health Professionals Follow-Up study, 1990–2010; Nurses’ Health Study, 1986–2006; and Nurses’ Health Study II, 1995–2015. Abbreviation: CVD, cardiovascular disease.

FIGURE 2

Estimated survival under hypothetical dietary interventions compared with no intervention in the Health Professionals Follow-Up study, the NHS, and the NHS II. Estimates are based on the parametric g-formula with baseline and prebaseline covariates: baseline age; BMI; smoking status; physical activities; parental history of myocardial infarction (<60 y); aspirin use; baseline diagnosis of hypertension or hypercholesterolemia; menopausal status (NHS/NHS II); menopausal hormone therapy (NHS/NHS II); prebaseline intakes of fruits and vegetables, fish, whole grains, processed meat, sugar-sweetened beverages, legumes/nuts/seeds, alcohol, and calories; and time-varying covariates: BMI; cigarette smoked per day; physical activity; aspirin use; menopausal status (NHS/NHS II); menopausal hormone therapy (NHS/NHS II); intakes of fruits and vegetables, fish, whole grains, processed meat, sugar-sweetened beverages, legumes/nuts/seeds, alcohol, and calories; incidences of hypertension, hypercholesterolemia, diabetes, cancer, nonfatal myocardial infarction; and time since report of each diagnosis. Abbreviations: AHA, American Heart Association; NHS, Nurses’ Health Study; NHS II, Nurses’ Health Study II.

FIGURE 3

Estimated (A) risk difference and (B) risk ratio of 20-y mortality for multi-food dietary strategies derived from the AHA 2020 Dietary Goals compared with no intervention in the HPFS (1990–2010), NHS (1986–2006), and NHS II (1995–2015). Estimates are based on the parametric g-formula with baseline and prebaseline covariates: baseline age; BMI; smoking status; physical activities; parental history of myocardial infarction (<60 y); aspirin use; menopausal status (NHS/NHS II); menopausal hormone therapy (NHS/NHS II); baseline diagnosis of hypertension or hypercholesterolemia; and prebaseline intakes of fruits and vegetables, fish, whole grains, processed meat, sugar-sweetened beverages, legumes/nuts/seeds, alcohol, and calories; and time-varying covariates: BMI; cigarettes smoked per day; physical activity; aspirin use; menopausal status (NHS/NHS II); menopausal hormone therapy (NHS/NHS II); intakes of fruits and vegetables, fish, whole grains, processed meat, sugar-sweetened beverages, legumes/nuts/seeds, alcohol, and calories; incidences of hypertension, hypercholesterolemia, diabetes, cancer, and nonfatal myocardial infarction; and time since report of each diagnosis. Abbreviations: AHA, American Heart Association; HPFS, Health Professionals Follow-Up Study; NHS, Nurses’ Health Study; NHS II, Nurses’ Health Study II.

FIGURE 4

Estimated (A) risk difference and (B) risk ratio of 20-y mortality under several single-food interventions derived from the AHA 2020 Dietary Goals compared with no intervention in the HPFS (1990–2010), NHS (1986–2006), and NHS II (1995–2015). Estimates are based on the parametric g-formula with baseline and prebaseline covariates: baseline age; BMI; smoking status; physical activities; parental history of myocardial infarction (<60 y); aspirin use; menopausal status (NHS/NHS II); menopausal hormone therapy (NHS/NHS II); baseline diagnosis of hypertension of hypercholesterolemia; and prebaseline intakes of fruits and vegetables, fish, whole grains, processed meat, sugar-sweetened beverages, legumes/nuts/seeds, alcohol, and calories; and time-varying covariates: BMI; cigarettes smoked per day; physical activity; aspirin use; menopausal status (NHS/NHS II); menopausal hormone therapy (NHS/NHS II); intakes of fruits and vegetables, fish, whole grains, processed meat, sugar-sweetened beverages, legumes/nuts/seeds, alcohol, and calories; incidences of hypertension, hypercholesterolemia, diabetes, cancer, and nonfatal myocardial infarction; and time since report of each diagnosis. Abbreviations: AHA, American Heart Association; HPFS, Health Professionals Follow-Up Study; NHS, Nurses’ Health Study; NHS II, Nurses’ Health Study II.