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Vitamin D Deficiency varies widely with season in young women, but not in old - April 2018

Older women do not have seasonal variations of vitamin D levels: a study from a southern country.

Menopause. 2018 Apr 9. doi: 10.1097/GME.0000000000001103. [Epub ahead of print]
Vallejo MS1, Blümel JE2, Lavín P3, Torres C1, Araos A1, Sciaraffia C1.


Santiago Women (33 degrees Latitude)

Age Summer: % <20 ngWinter: % < 20ng
20-395 %49 %
40-59 27 % 51 %
>60 40 % 40 %

Seems logical for 3 reasons

  1. Amount of vitamin D absorbed by the skin decreases with age
  2. Amount of time spent outdoors( near noon) probably decreases with age
  3. Amount of skin exposed when outdoors probably decreases with age

Most Vitamin D studies “adjust” vitamin D measurements with season
Do the studies vary the amount of adjustment with age?

The aim was to study whether the seasonal variation of vitamin D [25(OH)-D or calcidiol] is similar or different in younger and older women living in a southern country.

Measurement of serum 25(OH)-D concentration in 739 Chilean women aged 20 to 87 years, residents of Santiago (latitude: 33.4° South) who, during a routine gynaecological checkup, agreed to be evaluated.

The mean serum concentration of 25(OH)-D for the group was 24.1 ± 10.5 ng/mL. In women 20 to 39 years, the mean was significantly different from the mean of the ≥60 years old group (25.8 ± 10.6 ng/mL vs 23.9 ± 11.1 ng/mL; P < 0.02). Globally, 38.4% of participants had vitamin D deficiency and 36.1% insufficiency. A deficiency was present in 28.4% of the 20 to 39 years old, and in 43.9% in the ≥60 years old group (P < 0.004). In the whole group, a lower proportion (P < 0.0001) of vitamin D deficiency cases in the youngest women occurred during the summer (23.7%) in comparison to the winter (47.7%).
It was observed that the proportion of participants in the 20 to 39 years old group with vitamin D deficiency fell from 48.9% in winter to 4.9% in summer (P = 0.0001).
In the older groups, this change (less deficiency) is progressively smaller, 51.2% to 27.6% (P = 0.0020) in women 40 to 59 years old,
and it does not happen in women ≥60 years (40% with vitamin D deficiency).

Serum vitamin D deficiency [25(OH)-D or calcidiol] is highly prevalent in Santiago, especially in older women (≥60 y) throughout the year. In contrast, in younger women (<40 y), the vitamin D deficiency tends to disappear during summer. More epidemiological studies and targeted prevention actions on vitamin D deficiency are warranted.

PMID: 29634637 DOI: 10.1097/GME.0000000000001103

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