Seasonal variation in the serum 25-hydroxyvitamin D levels of young and elderly active and inactive adults in São Paulo, Brazil: The São PAulo Vitamin D Evaluation Study (SPADES).
OBJECTIVE
To evaluate the 25-hydroxyvitamin D [25(OH)D] concentrations in individuals in the city of São Paulo belonging to different age groups and exhibiting specific behavioral characteristics and to correlate the 25(OH)D concentration with the level of UV radiation (UVR).


METHODS
A total of 591 individuals were included, distributed as follows: 177 were living in institutions (NURSING, 76.2 ± 9.0 y old), 243 were part of the community elderly (COMMUNITY, 79.6 ± 5.3 y old), 99 were enrolled in a physical activity program targeting the elderly (ACTIVE, 67.6 ± 5.4 y old) and 72 were young (YOUNG, 23.9 ± 2.8 y old). Blood samples from all individuals were collected throughout the year. UVR measurements were taken by an official meteorology institution.


RESULTS
The UVR values varied throughout the year, following a sinusoidal-like pattern. Because of the Earth's orbit, we hypothesized that there would be cyclic patterns for the 25(OH)D and UVR values that repeat every 12 mo. The general formula is represented by the equation P1+P2⋅sin(-2⋅π12⋅(t-P3)) The mean 25(OH)D concentration and the amplitude of the variation were significantly higher for the YOUNG and ACTIVE groups than for the COMMUNITY and NURSING groups. The nadir for UVR was in June, whereas the nadir for the 25(OH)D concentration was in the spring, corresponding to a delay of one season.


CONCLUSIONS
There was seasonal variation in the 25(OH)D concentration for all the groups studied; however, the amplitude of the variation was higher for the groups of young and physically active people, possibly due to the higher level of sunlight exposure for these groups. The lowest 25(OH)D concentration was detected in the spring.
Department of Medicine; Endocrinology; UNIFESP (Universidade Federal de São Paulo); São Paulo, Brazil.
Sergio Setsuo
SS
Maeda
Department of Medicine; Endocrinology; UNIFESP (Universidade Federal de São Paulo); São Paulo, Brazil.
Gabriela Luporini
GL
Saraiva
Department of Medicine; Endocrinology; UNIFESP (Universidade Federal de São Paulo); São Paulo, Brazil.
Lilian Fukusima
LF
Hayashi
Department of Medicine; Geriatrics; UNIFESP (Universidade Federal de São Paulo); São Paulo, Brazil.
Maysa Seabra
MS
Cendoroglo
Department of Preventive Medicine; UNIFESP (Universidade Federal de São Paulo); São Paulo, Brazil.
Luiz Roberto
LR
Ramos
National Institute of Natural Resources; Universidade Federal de Itajubá; Itajubá, Brazil.
Marcelo de Paula
Mde P
Corrêa
Nuclear and Energy Research Institute (IPEN); Universidade de São Paulo (USP); São Paulo, Brazil.
Carlos
C
Henrique de Mesquita
Department of Medicine; Endocrinology; UNIFESP (Universidade Federal de São Paulo); São Paulo, Brazil.
Marise
M
Lazaretti-Castro
25-hydroxyvitamin D; delayed response; nadir; outdoor activity; seasonal variability; sun exposure; ultraviolet radiation