The global prevalence of diabetes among people aged 20~79 is expected to increase from 10.5% in 2021 to 12.2% in 2045 [1]. Furthermore, approximately 13.6% of people aged 30 and above in South Korea have diabetes; the majority (56.6%) are older adults aged 60 and older [2]. Various health concerns related to older adults with diabetes have been raised, one of which is nutritional problems, which are highly prevalent among people with diabetes of all ages [3, 4, 5]. Previous studies found that 18.5% to 21.2% of hospitalized older adults with diabetes were malnourished, and 33.1% to 39.1% were at risk of malnutrition [6, 7]. Moreover, community-dwelling older adults with diabetes might have a higher nutritional risk than those without diabetes [8].

Nutrition is a crucial factor for healthy aging [9] and an integral part of self-care for older adults with diabetes [10]. Malnutrition can be defined as a condition in which an imbalance of energy and nutrients adversely affects bodily functions and clinical outcomes. It is associated with a decline in other muscle, cognitive, digestive, and homeostatic regulatory functions [11, 12]; this term encompasses undernourishment and overnutrition [13]. Unlike malnutrition, nutritional risk refers to the risk of inadequate nutritional status caused by an imbalance between intake and metabolic needs [14, 15]. Nutritional deficiencies in older adults with diabetes can cause adverse health outcomes such as sarcopenia [16], frailty [17], risk of falls [18], diabetes complications, and mortality [19]. Therefore, good nutritional status is essential to prevent adverse outcomes and maintain a healthy life for older adults.

Several factors could put older adults with diabetes at a higher nutritional risk, such as restrictive eating habits to control blood glucose levels and age-related changes, including difficulty swallowing, changing sense of appetite, delayed gastric emptying, and dental problems [10, 20]. Previous studies have revealed that hospitalization, eating dependency, poor appetite, health status, and decreased physical function are associated with malnutrition in older adults [21]. Additionally, dementia, impaired functioning, chewing difficulties, swallowing difficulties, and older age are associated with malnutrition among institutionalized older adults [22]. Longitudinal studies have revealed that age, frailty, excessive polypharmacy, decreased physical function, and Parkinson’s disease affect malnutrition in older adults [23]. However, these studies focused on the general population of older adults.

Although a few studies regarding nutritional concerns have been conducted on older adults with diabetes [6, 7], they were performed in hospital settings and faced limitations in terms of identifying factors related to nutritional risk. In particular, visual impairment (VI) resulting from aging and diabetes complications is a risk factor for nutritional problems and may affect nutritional status in this population. A systematic review revealed that VI is linked to abnormal body mass index, difficulty shopping for meals, challenging meal preparation and eating, and visiting restaurants [24]. This implies that poor vision could be a barrier to adequate food intake. However, most of the included studies did not focus on individuals with diabetes. Older adults with diabetes have a higher prevalence of VI than the non-diabetic population [25]; however, empirical evidence regarding the association between VI and nutritional risk in this population is still limited.

Considering the importance and high prevalence of vision and nutritional problems among older adults with diabetes, this study aimed to identify the association between VI and nutritional risk among older adults with diabetes after controlling for other risk factors using nationally representative samples of older adults in South Korea.

We identified factors related to nutritional risk in a nationally representative sample of older South Korean adults. The main findings revealed that poor vision was associated with greater nutritional risk among older adults with diabetes. Although the relationship between VI and nutritional risk was weakened by the addition of other essential factors such as depression, dependent ADL status, and recent hospitalization, severe VI remained statistically significant.

Impaired vision could affect lifestyles, such as patients’ dietary habits, meal shopping, and restaurant use among people with diabetes and VI. Furthermore, diabetic patients with vision-related problems find it difficult to choose healthy food and find nutrition facts indicated on the surface of food packets [24]. They face difficulty accessing readable nutritional information, such as tactile materials or those with large prints [36], and they also face limitations in cooking. A previous study revealed that visually impaired people with diabetes expressed a lack of educational opportunities and a desire to learn to cook diabetes-friendly meals and calculate their optimal calorie and food consumption [37]. Older adults with diabetes and visual problems face more difficulties in maintaining a healthy diet and in other self-care domains such as glucose monitoring and exercise. Therefore, diabetes educators who care for older adults with diabetes and visual problems need to pay more attention to older adults with VIs’ eagerness to learn about diabetes self-care, cooking healthy meals, adhering to optimal calories, and challenges to self-care when they deliver diabetes education. Our results support the relationship between VI and nutritional risk; therefore, appropriate interventions to improve nutritional status in older adults with vision-related problems are needed, and visual characteristics should be considered during nutritional interventions in this population [38].

Among the covariates, depression, dependent ADL status, and hospitalization during the past year were strongly associated with nutritional risk, with depression being the most substantial factor. Previous studies have revealed that people with VI are more likely to have depression [39, 40]; depression is widely regarded as a barrier to diabetes management in older adults [41]. Since depression is prevalent among older adults with diabetes and is preventable and treatable, it should be screened for and prevented by incorporating it into diabetes self-management and nutritional education. Diabetes impairs mobility and ADL [42], with our study revealing that dependent ADL is a robust factor among the covariates for increasing nutritional risk, which is consistent with the findings of a previous longitudinal study [23]; recent hospitalization events are also a significant factor for nutritional risk. This means that older adults discharged from the hospital have a high nutritional risk for some time after discharge. It is obvious that hospitalization-related illnesses increase nutritional requirements and contribute to malnutrition among hospitalized older adults [43]. Nurses, doctors, and nutritionists must engage in multidisciplinary efforts to meet the nutritional requirements of older adults with diabetes who have been hospitalized recently. Such efforts may include additional nutritional support and careful discharge of nutritional plans.

Of the total number of older adults with diabetes in this study, 36.8% had moderate VI, and 4.2% had severe VI; these estimates were higher than for those without diabetes [44]. They were also higher than the low vision prevalence reported in the United States using best-corrected visual acuity [45] and 6.9% VI prevalence estimated by subjective measures [46]. This estimation in the current study may reflect a high prevalence of VI in the diabetic population [47] or may be attributed to our broad definition of VI. In this study, 42.3% of the participants were at nutritional risk. As nutrition is a crucial area in diabetes management, poor nutrition could worsen vision and other diabetes-related vascular complications [48]. Impaired vision increases the nutritional risk, and poor nutritional status increases the risk of diabetes-related complications, creating a vicious circle. Considering that many previous studies regarding VI and nutritional risk used a small sample size [24] and did not include older adults with diabetes, our findings with a large sample could provide evidence for the positive relationship between VI and nutritional risk in this population. Previous studies on diabetes patients focused on health outcomes, such as mortality and length of hospital stay, caused by nutritional risk among hospitalized patients [6, 7, 49]; however, our study investigated factors associated with nutritional risks, such as VI, which is a pervasive condition among diabetic patients. This study could provide insights into preventing nutritional risk in this population and fill the gaps in previous studies. Diabetes education and improving patients’ diabetes self-care management ability are important aspects of nursing interventions for persons with diabetes. Therefore, for diabetes educators and gerontological nurses, more attention to patients’ visual function will be needed. Appropriate screening, assessment, diagnosis, and treatment of older adults’ visual function and nutritional status should be considered in diabetes education to prevent both decreased vision and malnourishment in older adults with diabetes.

This study had some limitations. First, as this was a secondary data analysis, diverse variables related to known nutritional risk factors, laboratory variables, and diabetes-related factors, such as duration of diabetes and diabetes medication adherence, were not included in the original survey and, thus, excluded from this study. Therefore, future studies should consider these variables as covariates to ensure more rigorous findings. Second, the VI questions were based on self-reports rather than objective measurements. Third, this cross-sectional survey was unable to infer causal relationships. Nevertheless, this study had a large sample size that could provide data to estimate VI and nutritional prevalence among older adults with diabetes, and it can be generalized to South Korea.

Our findings suggest that severe VI positively correlates with nutritional risk in older adults with diabetes. Given the association between VI and nutritional risk, it is vital to prevent VI caused by exacerbation of diabetes through appropriate management. Additionally, tailored nutritional interventions considering visual characteristics, such as evaluating the participants’ preferences for materials and places and providing information to visually impaired older adults in accessible ways, are needed.