Assessment of the Dutch Healthy Diet index 2015 in the Lifelines cohort study at baseline

Dietary indices are useful measures to investigate associations between dietary intake and disease development. The Dutch Healthy Diet index 2015 (DHD2015-index), a measure of diet quality, assesses adherence to the 2015 Dutch dietary guidelines. We assessed the DHD2015-index in the Lifelines cohort study, and compared calculations from basic and detailed dietary intake data. This article replaces the retracted article that was published on 16 May 2022 [1].

Dietary intake was assessed with a specially developed Food Frequency Questionnaire (FFQ) called Flower-FFQ, which consists of one main questionnaire (heart-FFQ), which asks for intakes of major food groups, and three complementary questionnaires (petal-FFQs), which ask for detailed information on food types within major food groups of the heart-FFQ. The DHD2015-index was assessed using data from the total Flower-FFQ (for 56,982 participants), and using data from the heart-FFQ only (for 129,030 participants). Agreement between the two indices was assessed with correlation and cross-classification.

The median (25th-75th percentile) DHD2015-index score was 75 (65-85) for men and 81 (70-91) for women based on the Flower-FFQ, and 68 (58-77) for men and 73 (63-82) for women based on the heart-FFQ. The Kendall's tau-b correlation coefficient between the two scores was 0.67 for men and 0.66 for women. Cross-classification into quartiles of the DHD2015-index showed that 59-60% of participants were classified in the same quartile, 36-37% in the adjacent, and 4% in the non-adjacent.

Dietary data from the Flower-FFQ provide the most optimal information to assess the DHD2015-index. However, the DHD2015-index from the heart-FFQ showed good agreement with the index from the Flower-FFQ of ranking participants according to diet quality, and can be used when the DHD2015 index from the Flower-FFQ is not available.