Change in diet quality over 12 years in the 1946-1951 cohort of the Australian Longitudinal Study on women's health

Understanding patterns of dietary change over time can provide important information regarding population nutrition behaviours. The aims were to investigate change in diet quality over 12 years in a nationally representative sample of women born in 1946–1951 and to identify characteristics of women whose diet quality changed over time. The Australian Recommended Food Score (ARFS) was measured in 2001 (n = 10,629, mean age 52.1 years) and 2013 (n = 9115; n = 8161 for both time points) for the mid-aged cohort from the Australian Longitudinal Study on Women’s Health. Participants were categorised by tertiles of baseline diet quality and also classified as ‘diet quality worsened’ (ARFS decrease ≤ −4 points, n = 2361), ‘remained stable’ (−3 ≤ change in ARFS ≤ 3 points, n = 3077) or ‘improved’ (ARFS increase ≥ 4 points, n = 2723). On average, ARFS total and subscale scores remained relatively stable over time (mean [SD] change 0.3 [7.6] points) with some regression to the mean. Women whose diet quality worsened were more likely to be highly physically active at baseline compared with women whose diet quality improved (p < 0.001). Among women with poor diet quality initially (lowest baseline ARFS tertile, n = 2451, mean [SD] baseline ARFS 22.8 [4.5] points), almost half (47%, n = 1148) had not improved after 12 years, with women less likely to be in the healthy weight range (41% compared to 44%) and be never smokers (56% versus 62%, p < 0.05) compared with those whose diet improved. Diet quality remained relatively stable over 12 years’ follow up among mid-aged women. Almost half of those with poor baseline diet quality remained poor over time, emphasizing the need to target high-risk groups for nutrition interventions.