Serum vitamin D and subsequent occurrence of type 2 diabetes.
BACKGROUND
Low vitamin D status has been suggested as a risk factor for type 2 diabetes. Although the epidemiologic evidence is scarce, 2 recent studies have suggested an association. The present study investigated the relation of serum vitamin D with type 2 diabetes incidence using pooled data from these 2 cohorts.


METHODS
Two nested case-control studies, collected by the Finnish Mobile Clinic in 1973-1980, were pooled for analysis. The study populations consisted of men and women aged 40-74 years and free of diabetes at baseline. During a follow-up period of 22 years, 412 incident type 2 diabetes cases occurred, and 986 controls were selected by individual matching. Serum vitamin D (serum 25(OH)D) was determined from frozen samples, stored at baseline. Pooled estimates of the relationship between serum vitamin D concentration and type 2 diabetes incidence were calculated.


RESULTS
Men had higher serum vitamin D concentrations than women and showed a reduced risk of type 2 diabetes in their highest vitamin D quartile. The relative odds between the highest and lowest quartiles was 0.28 (95% confidence interval = 0.10-0.81) in men and 1.14 (0.60-2.17) in women after adjustment for smoking, body mass index, physical activity, and education.


CONCLUSIONS
The results support the hypothesis that high vitamin D status provides protection against type 2 diabetes. Residual confounding may contribute to this association.
Knekt
Paul
P
National Public Health Institute, Department of Health and Functional Capacity, Mannerheimintie 166, 00300 Helsinki, Finland. paul.knekt@ktl.fi
Laaksonen
Maarit
M
Mattila
Catharina
C
Härkänen
Tommi
T
Marniemi
Jukka
J
Heliövaara
Markku
M
Rissanen
Harri
H
Montonen
Jukka
J
Reunanen
Antti
A
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000453:epidemiology; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D008019:Life Style; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017678:Sex Distribution; D014807:Vitamin D / Q000097:blood*
D014807:Vitamin D