Abstract
Suboptimal nutrition in older adults is a major cause of morbidity, physical and cognitive decline, frailty, anemia, and reduced quality of life. Studies in other western countries show that malnutrition is common in residential aged-care, affecting up to 85% of residents; however, there is little data available regarding the nutritional status of New Zealand aged-care residents. Information on nutritional status, lifestyle and health characteristics specific to aged-care residents in New Zealand is needed to identify risks and ensure interventions are developed in culturally acceptable and appropriate ways to meet the needs and requirements of older New Zealand adults. The purpose of the present study was, therefore, to evaluate the prevalence and determinants of malnutrition, frailty and select micronutrient status of New Zealand aged-care residents.
Three-hundred and nine adults aged 65 years or over were recruited from 16 aged-care facilities throughout New Zealand. Residents were eligible to participate if they had been in rest-home level care for 12 weeks or longer. Dietary, socio-demographic, health and biochemical data was collected in two time periods; February to April 2014 and July to September 2014.
Our results showed that 6.8% of residents were malnourished with a further 39% identified as being at risk of malnutrition. A larger proportion of participants were classified as prefrail (33%) or frail (50%). Malnourished and frail participants had lower intakes of energy and protein and poorer physical function yet differed distinctively with regards to other factors. For example, malnutrition was associated with lower circulating concentrations of leptin, but was not significantly associated with inflammation status, frailty or cognition. In contrast, frail participants had higher concentrations of both the acute phase proteins (CRP and AGP) as well as the pro-inflammatory cytokine IL-6; however, only IL-6 concentrations were significantly higher across the frailty subgroups (P = 0.011). We also observed that few frail participants received oral nutrition supplements or feeding assistance in comparison to malnourished participants. Lack of awareness among aged-care staff regarding the relationship between adequate nutritional intake and frailty may be present and requires further investigation.
With regards to micronutrient status, we observed significant differences in iron, zinc and selenium concentrations with adjustment for inflammatory biomarkers. The presence of inflammation among residents was high, with 40% having elevated CRP and/or AGP concentrations and 37% of participants having higher than normal IL-6 – a marker of both acute and chronic inflammation. The regression adjustment for inflammation using IL-6 as the inflammatory marker provided the greatest adjustment in the concentrations of serum ferritin, sTfR, TBI and plasma zinc and selenium as compared to CRP and AGP. Consequently, almost three quarters (72%) of participants were identified as zinc deficient and more than one third (39%) as being selenium deficient. The prevalence of iron deficiency, however, was virtually absent (1%), despite 32% having low hemoglobin concentrations indicative of anemia. Anti-secretory medications, hepcidin and interleukin-6 were negatively associated with hemoglobin, whereas positive associations were observed with plasma zinc and total body iron (P < 0.05). Notably, a mediating effect of zinc on the association between selenium and haemoglobin was identified, emphasising the complex interplay of factors that impact anemia in older adults.
Vitamin D status among participants was quite high [25(OH)D 89.9 nmol/L (95% CI 85.2, 95)] mostly due to the uptake of a prescribed funded supplement [50 000 IU (1.25 mg) per month] by three-quarters of this cohort. Of those taking a funded supplement, only 1.5% had serum 25(OH)D < 50 nmol/L compared to 65.3% of non-supplement users. Higher 25(OH)D concentration was positively associated with residing at lower latitude, being female, having a longer duration of aged-care residency and raised serum α1-acid glycoprotein. Supplemental vitamin D from all sources was the strongest predictor, increasing serum 25(OH)D by more than 70 nmol/L. Concerningly, 22% of participants had serum 25(OH)D concentrations > 125 nmol/L.
In conclusion, with increasing numbers of older adults requiring residential care services, optimising the nutritional status, and thus the wellbeing of older adults, is an important public health issue. Our findings indicate that frailty and malnutrition are present in New Zealand aged-care residents and were significantly associated with energy and protein intakes. We also confirmed that the inflammatory state of ageing and infection alters the concentrations of circulating micronutrient biomarkers and as such, should be interpreted with caution. These inflammation-related changes do not necessarily reflect micronutrient status, and adjustment for inflammation is necessary if the prevalence of deficiency states is not to be overestimated.
Our results also highlight the multifactorial nature of micronutrient status and anemia in older adults, and that multiple micronutrients influence haemoglobin concentrations and, thus anemia. Further research is needed to determine appropriate nutrition support interventions to correct such conditions and deficiencies and which will ameliorate the progression of prefrailty and malnutrition risk in residential aged-care.