Ambient UVB Dose and Sun Enjoyment Are Important Predictors of Vitamin D Status in an Older Population

Abstract

UVB-induced skin synthesis is considered the key source of vitamin D, yet exposure to UVB is poorly accounted for in epidemiological studies. The aim of this study was to examine the association of serum 25-hydroxyvitamin D [25(OH)D] concentration with accurately measured ambient UVB dose, sun enjoyment, supplements, and other factors. An all-Irish cohort of community-dwelling participants aged >60 y [median age: 73; 67% female; median 25(OH)D: 54.5 nmol/L] was used. Participants from this large, cross-sectional study completed a questionnaire to provide information on demographic factors and lifestyle (including supplement use and sun enjoyment). The Tropospheric Emission Monitoring Internet Service database was used to extract the daily ambient UVB dose at wavelengths that could induce vitamin D synthesis (D-UVB) over Ireland (latitude: 51°N-55°N). Blood sampling occurred throughout the year. Ambient exposure at the place of residence was calculated for each participant individually. Associations between determinants and serum 25(OH)D concentration were examined in a multivariate model. Random forest analysis was used to establish prediction models of vitamin D deficiency, and area under the curve (AUC) is shown. In total, 5138 individuals were included. Median D-UVB was 63 mJ/cm, which varied between seasons and latitudes, despite the small latitude differential. Vitamin D supplementation (β = 27.7; < 10 × 10), D-UVB (β = 1.58 per 1000 mJ/cm; < 10 × 10), and sun enjoyment (β = 6.6; < 0.001) were strongly positively associated with serum 25(OH)D. Those who avoided sunshine were largely at risk of deficiency (<40 nmol/L), whereas those who enjoyed sunshine tended to be vitamin D sufficient (≥50 nmol/L). D-UVB and sun enjoyment improved prediction of deficiency in non-supplement-taking individuals; the overall AUC improved by 3.5%. D-UVB and sun enjoyment are important predictors of vitamin D status, even in this elderly population at northern latitudes. Accurate estimation of ambient UVB can help to further clarify the role of other determinants of vitamin D status and inform sunshine recommendation guidelines.

Annual Ambient UVB at Wavelengths that Induce Vitamin D Synthesis is Associated with Reduced Esophageal and Gastric Cancer Risk: A Nested Case–Control Study

“…Additionally, we did not have information on the duration individuals resided at the residence given; this is a limitation of this study as we calculated D-UVB dose based on their location of residence. We also unfortunately did not have 25(OH)D concentration, although strong relationship between D-UVB and 25(OH)D has been shown previously (15,44). While 25(OH)D is the best marker of vitamin D status at the time of blood draw, this provides little information about the average exposure over a prolonged period of time cancer takes to develop (45).…”

“…This D‐UVB measure has also been corrected for many important factors which can considerably alter the D‐UVB dose reaching earth, such as cloud cover, ozone column and altitude. The strength of a similar D‐UVB measurement has been discussed in detail previously , and the D‐UVB used in this paper is of even greater special and temporal resolution . Furthermore, this ambient UVB dose took into account annual D‐UVB to get a “long‐term average” UVB dose for each individual, rather than a seasonally biased estimate, which would have been the case if a point estimate of vitamin D, such as 25(OH)D, was utilized.…”

“…‡ ‡ Percentage of all controls. been discussed in detail previously (15), and the D-UVB used in this paper is of even greater special and temporal resolution (22). Furthermore, this ambient UVB dose took into account annual D-UVB to get a "long-term average" UVB dose for each individual, rather than a seasonally biased estimate, which would have been the case if a point estimate of vitamin D, such as 25 (OH)D, was utilized.…”

Vitamin D Status in Japanese Adults: Relationship of Serum 25-Hydroxyvitamin D with Simultaneously Measured Dietary Vitamin D Intake and Ultraviolet Ray Exposure

“…Scragg et al also used this dosimeter, but also did not investigate vitamin D intake [40]. O'Sullivan et al estimated the daily ambient UVB dose for each participant in their study by using irradiated UV energy at various geographical points in Ireland and the residential address of the participants, and reported a relationship between it and serum 25(OH)D concentration [41]. Their estimation method differed from ours, which directly measured UV energy on the participants' arms.…”

Seasonality of birth affects paediatric coeliac disease

“…A number of environmental factors, such as infections, vitamin exposure , the use of proton pump inhibitors , short duration of breastfeeding, parental smoking and changes in the gut microbium , have been reported to be involved in the pathogenesis of CD . It has also been suggested that ultraviolet B radiation influences the synthesis of vitamin D , which has been associated with the development of future CD . A study in the United States found that living in north versus south latitudes were associated with CD and this indicated that low levels of global radiation and cold weather could serve as risk factors for future CD.…”