Stability of the Framingham Nutritional Risk Score and its component nutrients over 8 years: The Framingham Nutrition Studies

BACKGROUND / OBJECTIVES: Diet quality indices are increasingly used in nutrition epidemiology as dietary exposures in relation to health outcomes. However, literature on long-term stability of these indices is limited. We aimed to assess the stability of the validated Framingham Nutritional Risk Score (FNRS) and its component nutrients over 8 years as well as the validity of the follow-up FNRS. SUBJECTS / METHODS: Framingham Offspring/Spouse Study women and men (n=1 734) aged 22-76 years wwver 8 years. Individuals' nutrient intake and nutritional risk scores were assessed using 3-day dietary records administered at baseline (1984-1988) and at follow-up (1992-1996). Agreement between baseline and follow-up FNRS and nutrient intakes was evaluated using Bland-Altman method; stability was assessed using intra-class correlation (ICC) and weighted Kappa statistics. The effect of diet quality (as assessed by the FNRS) on cardiometabolic risk factors was evaluated using ANCOVA. RESULTS: Modest changes from baseline (≤15%) were observed in nutrient intake. Stability coefficients for the FNRS (ICC: women=0.49; men=0.46; P<0.0001) and many nutrients (ICC ≥0.3) were moderate. Over half of women and men (58%) remained in the same or contiguous baseline and follow-up quartile of the FNRS and few (3-4%) shifted >1 quartile. The FNRS was directly associated with BMI in women (P<0.01) and HDL-cholesterol among both women (P<0.001) and men (P<0.01). CONCLUSION: The FNRS and its constituent nutrients remained relatively stable over 8 years of follow-up. The stability of diet quality has implications for prospective epidemiological investigations.