Diet Diversity Score Elderly Living in Tehran City and its Related Demographic and Socio-economic Factors, 2017 and 2021: A Longitudinal Study

Background and Objectives: Based on available evidence, dietary diversity may change with aging. Decreases in dietary diversity score of the elderly people may be affected by various factors, including their demographic and socioeconomic status. The aim of this study was to assess and compare demographic and socioeconomic statuses associated with dietary diversity score (DDS) of the elderly people living in Tehran City, in 2017 and 2021. Materials and Methods: In this longitudinal study, 368 elderly people [204 (55.4%) women and 164 (44.6%) men] over 60 years of age were assessed at two-time points of 2017 and 2021. Demographic and socioeconomic information were assessed using a questionnaire and dietary intake was assessed using 24-h food recall questionnaires for two non-consecutive days. Dietary diversity score was calculated based on Kant method. Statistical analysis was carried out using R software and mixed effect model. Results: The mean ±SD (standard deviation) of age of the elderly people was 67.06 y ±5.52 and 70.89 y ±6.48 in 2017 and 2021, respectively. Moreover, mean ±SD of the elderlies’ dietary diversity score in 2017 (5.07 ±1.20) was higher than that of 2021 (4.94 ±1.09) (p < 0.05). After adjusting the effects of all demographic and socioeconomic variables in the model, higher education compared to under-diploma education had direct relationships with dietary diversity scores  (β = 0.794; p < 0.001). Due to the longitudinal design of the study, differences in the effects of the higher education on dietary diversity scores between 2017 and 2021 was -0.151, meaning that these effects decreased by 0.151 in 2021, compared to the baseline year; however, non-significantly (β = -0.151; p = 0.416). Elderly people living in households with size of three or more (β = 0.614; p < 0.01) had higher dietary diversity score compared to those who lived alone (β = 0.652; p < 0.05). Differences in the effects of households size of three or greater on DDS between 2017 and 2021 was non-significance (β = -0.091; p = 0.712). Having middle (β = 0.971; p < 0.001) and high (β = 0.417; p < 0.01) incomes was directly linked to higher DDS compared to low incomes. Differences in the effects of income levels on dietary diversity scores between the two period of the study was not significance (p > 0.05). Conclusion: findings indicated that having university education, higher income and living in households with the size of 3 or more were the most important demographic and socioeconomic characteristics associated with higher DDS in elderly people living in Tehran City. Studies with longer periods of time can reveal more definitive results regarding the effects of socioeconomic statuses on diet quality of elderly people.