Development of the ‘Healthy Eating Index for Older People’ to Measure Adherence to Dietary Guidelines in Healthy Older New Zealand Adults

This study aimed to develop the ‘Healthy Eating Index for Older People’ (the index), based on New Zealand dietary guidelines, and measures the validity and reproducibility of a food frequency questionnaire (FFQ) to derive the index scores in older adults. In Auckland, New Zealand, participants (community-dwelling adults aged 65–74 years, [n = 273, 36% male]) completed a 109-item FFQ administered one month apart (FFQ1, FFQ2), with a four-day food record (4-DFR) collected in between. Adherence to the guidelines was scored using the index, comprising a total score (maximum = 100) and two sub-scores: adequacy (maximum = 60) and moderation (maximum = 40). A comparison of FFQ1 and FFQ2 determined reproducibility, and FFQ1 and 4-DFR determined validity. Higher index scores (from FFQ1) were associated with higher intakes of protein, fibre, vitamins and minerals and lower intakes of alcohol and saturated fats (nutrients from 4-DFR) after adjusting for age and sex (all p < 0.001). Total index and sub-indices correlation coefficients ranged from 0.42 to 0.77 (all p < 0.001); weighted kappa values ranged from 0.35 to 0.67; and mean differences were all <10% of FFQ1 for reproducibility and validity. The Bland–Altman analysis showed no bias for the total index score for reproducibility and validity. However, with validation, the sub-index scores became less reliable as food intake increased (p < 0.05). The index applied to the FFQ demonstrated good construct validity and reproducibility. Relative and absolute validity were acceptable, though caution is required when using the absolute sub-index scores. The index is suitable for measuring total diet quality in older New Zealand adults.