AIMS: To explore the effects of seasonal variation on the diagnosis of vitamin D sufficiency and to determine whether age, gender, and ethnicity modify these effects. METHODS: 21,987 adults had a measurement of serum 25-hydroxyvitamin D (25OHD) at Labplus, Auckland City Hospital, between January 2002 and September 2003, and sine curves were fitted for 25OHD versus day of year to predict the 25OHD nadir for each individual. RESULTS: 48% (range: 30-63%) of individuals had 25OHD <50 nmol/L in the month of measurement, but 63% were predicted to have 25OHD <50 nmol/L in late winter or early spring based on expected seasonal variation. The 25OHD levels required to ensure 25OHD levels >50 nmol/L throughout the year varied substantially by season (in summer at least 60-75 nmol/L), and tended to be higher in men than women, decrease with age, and vary with ethnicity. Mean 25OHD levels were very low (<40 nmol/L) in people of Indian, Middle Eastern, and African descent. CONCLUSION: Seasonal variation in 25OHD affects the diagnosis of vitamin D sufficiency. Clinicians should consider the month of sampling when interpreting the results of 25OHD measurements. In New Zealand, a summertime 25OHD <60-75 nmol/L is generally required to ensure year-round 25OHD levels <50 nmol/L.
AIMS: To explore the effects of seasonal variation on the diagnosis of vitamin D sufficiency and to determine whether age, gender, and ethnicity modify these effects. METHODS: 21,987 adults had a measurement of serum 25-hydroxyvitamin D (25OHD) at Labplus, Auckland City Hospital, between January 2002 and September 2003, and sine curves were fitted for 25OHD versus day of year to predict the 25OHD nadir for each individual. RESULTS: 48% (range: 30-63%) of individuals had 25OHD <50 nmol/L in the month of measurement, but 63% were predicted to have 25OHD <50 nmol/L in late winter or early spring based on expected seasonal variation. The 25OHD levels required to ensure 25OHD levels >50 nmol/L throughout the year varied substantially by season (in summer at least 60-75 nmol/L), and tended to be higher in men than women, decrease with age, and vary with ethnicity. Mean 25OHD levels were very low (<40 nmol/L) in people of Indian, Middle Eastern, and African descent. CONCLUSION: Seasonal variation in 25OHD affects the diagnosis of vitamin D sufficiency. Clinicians should consider the month of sampling when interpreting the results of 25OHD measurements. In New Zealand, a summertime 25OHD <60-75 nmol/L is generally required to ensure year-round 25OHD levels <50 nmol/L.
Authors: Robert K R Scragg; Alistair W Stewart; Richard L McKenzie; Anthony I Reeder; J Ben Liley; Martin W Allen Journal: J Expo Sci Environ Epidemiol Date: 2016-09-07 Impact factor: 5.563
Authors: Michael C Sachs; Abigail Shoben; Gregory P Levin; Cassy Robinson-Cohen; Andrew N Hoofnagle; Nancy Swords-Jenny; Joachim H Ix; Matthew Budoff; Pamela L Lutsey; David S Siscovick; Bryan Kestenbaum; Ian H de Boer Journal: Am J Clin Nutr Date: 2013-04-24 Impact factor: 7.045
Authors: Philippe Vuistiner; Valentin Rousson; Hugues Henry; Pierre Lescuyer; Olivier Boulat; Jean-Michel Gaspoz; Vincent Mooser; Peter Vollenweider; Gerard Waeber; Jacques Cornuz; Fred Paccaud; Murielle Bochud; Idris Guessous Journal: Biomed Res Int Date: 2015-09-01 Impact factor: 3.411