Iodine intake as a possible cause of discontinuous decline in sperm counts: a re-evaluation of historical and geographic variation in semen quality.
In order to examine whether iodine supplements may have caused a global decline in sperm concentrations during the past several decades, the synchronicity of the decline in mean sperm counts and the introduction of iodine supplements was analyzed statistically. A positive correlation between the incidence of thyroid disease and sperm counts has been detected in Europe. In addition, it has been shown that sperm counts began falling around 1965 in the United States, 40 years after iodine supplements were introduced. Mean sperm counts before and after 1965 were 111 x 10(6)/ml and 70 x 10(6)/ml, respectively, in calculations weighted by the number of subjects included in each individual publication. The timing of the declines coincided with the introduction of iodine supplements in the United States, France, and the United Kingdom. The implications are that the global decline in sperm concentrations may be caused by iodine intake. Geographical variation in the types of sperm count decline also appears to be present.
Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Kita-ku N18W9, Sapporo 060-0818, Japan.
Kentaro Q
KQ
Sakamoto
Mayumi
M
Ishizuka
Akio
A
Kazusaka
Shoichi
S
Fujita
D000328:Adult; D019587:Dietary Supplements / Q000009:adverse effects / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000009:adverse effects*; D016014:Linear Models; D008297:Male; D012661:Semen / Q000502:physiology; D013076:Sperm Count / Q000706:statistics & numerical data; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D013959:Thyroid Diseases / Q000188:drug therapy* / Q000453:epidemiology / Q000517:prevention & control; D014481:United States / Q000453:epidemiology
D007455:Iodine