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Seasonal reduction in vitamin D level persists into spring in NSW Australia: implications for monitoring and replacement therapy
Author(s) -
Boyages Steven,
Bilinski Kellie
Publication year - 2012
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.2012.04398.x
Subject(s) - medicine , context (archaeology) , vitamin d deficiency , vitamin d and neurology , demography , socioeconomic status , ambulatory , population , environmental health , geography , sociology , archaeology
Summary Context Seasonal variation in 25‐hydroxyvitamin D [25 OHD ] status and its relationship to gender, age, socioeconomic and geographic determinants in A ustralians has not been described in large biomedical sampling cohorts. Objectives To analyse 25 OHD levels in all primary tests undertaken consecutively in a 2‐year period to determine the prevalence of 25 OHD deficiency and its relation to patient setting, gender, age, season, urban or rural residency, socioeconomic status, latitude and longitude. Design We assessed 24 819 ambulatory and inpatient samples taken from the largest reference laboratory in NSW , A ustralia between 01 July 2008 and 30 July 2010. Main outcome measures Serum 25 OHD was measured using chemiluminescent immunoassay. Vitamin D deficiency was defined as 25 OHD <50 n m . Results Median 25 OHD was 54 n m ranging from 63 n m in summer to 44 n m in spring and was lowest in inpatient women (49 n m ) and highest in ambulatory men (64 n m ). Mean 25 OHD peaked in J anuary (67 n m ) and reached a nadir in A ugust/ S eptember (39 n m ). During summer, 36% subjects overall had a level below 50 n m , increasing to 58% in spring. The highest prevalence of deficiency occurred in female inpatients (42% in summer and 62% in spring). Factors associated with lower 25 OHD included being tested in spring, an inpatient, female, aged 20–39 or >79 years, socioeconomically disadvantaged and from a major city. Conclusion This cross‐sectional study demonstrates the extent and duration of 25 OHD deficiency is greater than expected, and particular individuals are at higher risk. Our findings imply that supplementation guidelines need to be modified and strengthened.