The Association between Poor Diet Quality, Physical Fatigability and Physical Function in the Oldest-Old from the Geisinger Rural Aging Study

Abstract

More perceived physical fatigability and poor diet quality are associated with impairments in physical function in older adults. However, the degree to which more perceived fatigability explains the association between poor diet quality and low physical function is unknown. We examined this relationship in 122 (66F, 56M) of the oldest-old participants from the Geisinger Rural Aging Study (GRAS). We used 24-h dietary recalls to assess the Healthy Eating Index (HEI), the Pittsburgh Fatigability Scale (PFS, 0-50) to assess perceived physical fatigability, and the PROMIS Physical Function 20a* to assess physical function. We grouped participants into three age categories: 80-84 (n = 51), 85-89 (n = 51), and 90+ (n = 20) years. Multiple linear regression revealed that a lower HEI was associated with higher PFS Physical score after adjusting for age group, sex, body mass index, and the number of medical conditions (p = 0.001). Several macro- and micro-nutrient intakes were also lower in those reporting more (≥15) compared to less (<15) perceived physical fatigability. Mediation analysis revealed that PFS Physical scores explained ~65% (p = 0.001) of the association between HEI total score and PROMIS19 Physical Function score. Poor diet quality may contribute to more perceived physical fatigability, which could exacerbate impairments in the oldest-old's physical function.

Keywords: aging; fatigue; frailty; geriatrics; healthy eating index; macronutrients; micronutrients; nutrition; physical function; protein.

Figure 1

Leverage plots displaying the effect of the Healthy Eating Index (HEI) on Pittsburgh Fatigability Scale (PFS) Physical score (A) and PROMIS19 Physical Function (B) score after adjusting for age, sex, BMI, and the total number of medical conditions in a subset of 122 oldest-old participants from the Geisinger Rural Aging Study.

Figure 2

(A) shows the statistical mediation analysis for the associations of the lower Healthy Eating Index, more self-reported physical fatigability, on lower self-reported physical function through in a subset of 122 oldest-old participants from the Geisinger Rural Aging Study. (B) shows the statistical mediation analysis for the associations of the lower Healthy Eating Index—protein, more self-reported physical fatigability, on lower self-reported physical function through in a subset of 122 oldest-old participants from the Geisinger Rural Aging Study. The dependent (outcome) variable was set as the PROMIS19 Physical Function score, while the independent variable was set as the HEI total (A) or HEI protein (B), and the mediating variable was set as the Pittsburgh Fatigability Scale (PFS) Physical score. The models were also adjusted for the age group, sex, BMI, and the total number of medical conditions. The 95% confidence intervals (95% CI) were based on bootstrapping (1000 samples).