Vitamin D status of Maori and non-Maori octogenarians in New Zealand: a Cohort Study (LiLACS NZ)

Background and Objectives: This study assessed vitamin D status and its determinants in a cohort of octogenarians living within New Zealand's Bay of Plenty and Lakes Districts. Methods and Study Design: Serum 25-hydroxyvitamin D [25(OH)D] concentration was measured in 209 Maori (aged 80-90 years) and 357 non-Maori (85 years), along with demographic, lifestyle, supplement use and other health data. Results: Mean [95% CI] 25(OH)D concentration was 69 [67 to 72] nmol/L, with 15% >100 nmol/L and 6 individuals >150 nmol/L. Concentrations in Maori (59 [55 to 62] 4 nmol/L) were lower than in non-Maori (75 [72 to 78] nmol/L; p<0.001), a difference maintained when adjusted for day-of-year measured. Vitamin D supplementation was reported by 98 participants (18%): including a greater proportion of women (24%) than men (11%; p<0.001) and of non-Maori (24%) than Maori (7%; p<0.001). Of those taking vitamin D, 49% took high oral doses (>= 25 mu g/day or equivalent) and five individuals took >50 mu g/day. Vitamin D supplement use strongly and independently predicted seasonally-adjusted 25(OH)D concentration and was associated with 28 nmol/L higher levels than non-use. Other predictors included Maori ethnicity (10 nmol/L lower concentration than for non-Maori), and female gender (11 nmol/L lower). Conclusions: Vitamin D status in New Zealand octogenarians appears higher than previously reported, particularly in non-Maori compared to Maori. Prescribed and non-prescribed oral vitamin D supplementation is prevalent in this group and a strong indicator of vitamin D status.