Vitamin D status of Māori and non-Māori 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 Māori (aged 80-90 years) and 357 non-Māori (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 Māori (59 [55 to 62] 4 nmol/L) were lower than in non-Māori (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-Māori (24%) than Māori (7%; p<0.001). Of those taking vitamin D, 49% took high oral doses (>=25 μg/day or equivalent) and five individuals took >50 μg/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 Māori ethnicity (10 nmol/L lower concentration than for non-Māori), and female gender (11 nmol/L lower).

CONCLUSIONS: Vitamin D status in New Zealand octogenarians appears higher than previously reported, particularly in non-Māori compared to Māori. Prescribed and non-prescribed oral vitamin D supplementation is prevalent in this group and a strong indicator of vitamin D status.