B-vitamin status and homocysteine in older adults in residential aged care facilities in New Zealand: a cross-sectional study

Abstract

Background: Adequate micronutrient status plays a key role in preventing or delaying the progression of age-related diseases. However, the physiological and psychosocial changes associated with ageing increase the risk of nutritional deficiencies. Few studies have investigated the micronutrient status of older adults in New Zealand. In particular, a number of B-vitamins may be at increased risk of suboptimal status leading to an increase in homocysteine concentrations – a key intermediate of one-carbon metabolism commonly associated with age-related diseases. Objectives: The aim of the study was to determine the status of folate, riboflavin, vitamin B6 and vitamin B12, and the prevalence of hyperhomocysteinemia in older New Zealand adults living in residential aged care facilities (RACF). Furthermore, the relationship between homocysteine and B-vitamin status (including betaine and choline), along with existing conditions of depression, diabetes and stroke were investigated. Design and method: In this cross-sectional study, blood samples were collected from 263 older adults (> 65 years) living in 16 RACF across New Zealand. Detailed medical history, including medication use and anthropometric measurements, were collected. The Geriatric Depression Scale-Short Form (GDS-SF) and Mini Nutritional Assessment-Short Form were used to screen for depression and malnutrition, respectively; and the Survey of Health, Ageing and Retirement in Europe Frailty Instrument (SHARE-FI) was used to score frailty. Fasting blood samples were analysed for serum folate, serum vitamin B12, riboflavin and vitamin B6, as well as plasma homocysteine, betaine and choline. Inflammatory markers [C-reactive protein (CRP), alpha-1-acid glycoprotein (AGP) and interleukin-6 (IL-6)] were also measured. Results: The mean age of participants was 85 years; the majority were women and of New Zealand European descent. The average length of RACF stay was 32 months. Fewer than 10% of participants were malnourished, 7% were underweight and 52% were classified as frail. More than half of the sample population had hypertension, 25% had diabetes, 24% had a history of a cerebrovascular accident (CVA) or transient ischemic attack (TIA), and 30% were classified as being depressed (GDS-SF > 5). Vitamin B6 (EAST-AC > 1.85) had the highest prevalence of deficiency (36.5%) among participants followed by serum folate 8.9% (< 6.8 nmol/L) and vitamin B12 0.4% (< 148 pmol/L). Riboflavin deficiency (EGR-AC > 1.4) was not present among our sample population. Nonetheless, marginal status of vitamin B12 (148-221 pmol/L) and riboflavin (EGR-AC 1.2-1.4) existed in 7.6% and 4.1%, respectively. Over two- thirds of participants exhibited elevated homocysteine (> 15 mol/L). Multiple linear regression showed that homocysteine was negatively associated with folate, vitamin B12, and betaine (p < 0.001), and positively associated with choline (p < 0.001), controlling for renal function (estimated glomerular filtration rate), inflammation (IL-6) and diuretic use. No association was found between homocysteine and diabetes, stroke and depression. Conclusions: In older adults living in RACF in New Zealand, the prevalence of folate, vitamin B12 and riboflavin deficiency was low, while vitamin B6 deficiency was high. Further work is needed to confirm our findings, in particular vitamin B6 due to the known assay limitations. Given the high prevalence of hyperhomocysteinemia and its negative association with folate and vitamin B12, it is unknown whether an increase in the present adequate status would lower circulating homocysteine levels.