Sood, SReghunandanan, RSingh, UReghunandanan, VSingh, P I1993-08-012009-05-291993-08-012009-05-291993-08-01Sood S, Reghunandanan R, Singh U, Reghunandanan V, Singh PI. Circanual variation of sperm count and motility in men. Indian Journal of Medical Sciences. 1993 Aug; 47(8): 197-200http://imsear.searo.who.int/handle/123456789/65967Seasonal variation in rhythmicity of spermatogenesis might be due to external temperature fluctuation which could partially be responsible for decreased sperm counts in summer. Other factor like exposure to light might contribute for the reduction in sperm counts. These facts should be taken into account before diagnosing male fertility.engAdultBiological ClocksFertility --physiologyHumansMaleMiddle AgedSeasonsSperm CountSperm MotilityJournal Article