Trying for a baby? Now's the best time: Men have healthier sperm in winter and spring

Human sperm is at its healthiest in winter and in early spring, say scientists



Semen made during the winter contains more sperm and it is faster moving

Sperm quality declines steadily from spring onwards

Reasons not yet clear but may be due to colder temperatures - allowing better environment for sperm



Men have healthier sperm in winter and early spring than in summer, new research has revealed.



Israeli scientists studied samples from more than 6,000 men who were being treated for infertility.



They found sperm in greater numbers, with faster swimming speeds, and fewer abnormalities, in semen made during the winter.



The sperm declined steadily in quality from spring onwards.



Human sperm is generally at its healthiest in winter and early spring, new Israeli research reveals

The researchers say this may explain why there are so many babies born in the autumn.

The reason why sperm appears to be healthier in winter isn't yet clear. One theory is sperm is affected by warn temperatures.

In animal studies, seasonal changes in sperm production and fertility have been linked to factors ranging from temperature, to length of daylight exposure and hormone variations.

Writing in the American Journal of Obstetrics & Gynaecology, the researchers said that if there is a seasonal pattern, that knowledge may ‘be of paramount importance, especially in couples with male-related infertility struggling with unsuccessful and prolonged fertility treatments.’

For the new study, Professor Eliahu Levitas and his colleagues, from Ben-Gurion University of the Negev, collected and analysed 6,455 semen samples from men at their fertility clinic between January 2006 and July 2009.

Of those, 4,960 were found to have normal sperm production, and 1,495 had abnormal production, such as low sperm counts.



The World Health Organisation defines anything over 16 million sperm per millilitre of semen as a normal sperm count.



Taking into account the approximately 70 days it takes for the body to produce a sperm cell, the researchers found that men with normal sperm production had the healthiest sperm in the winter.



The researchers found sperm in greater numbers, with faster swimming speeds, in semen made during the winter

For example, those men produced about 70 million sperm per millilitre of semen during the winter.



About five per cent of those sperm had ‘fast’ motility, or swimming speed, which improves a couple's chance of getting pregnant.



That compared to the approximately 68 million sperm per millilitre the men produced in the spring, of which only about three per cent were ‘fast’.



For men with abnormal sperm production, however, the pattern did not hold.



Those men showed a slight trend toward better motility during the autumn and made the largest percentage of normal shaped sperm - about seven per cent - during the spring.



Previous studies, mostly in animals, have found similar results in line with those species' breeding seasons, Dr Edmund Sabanegh, a urologist who was not involved in the new research, told Reuters Health.



‘The hard part of this is really sorting out what factor is accounting for this,’ said Dr Sabanegh, the chairman of the urology department at Ohio's Cleveland Clinic.



In animal studies, seasonal changes in sperm production and fertility have been linked to factors ranging from temperature, to length of daylight exposure and hormone variations.



Previous research has found that human sperm counts around the world are falling.



While no one knows why, theories range from a more sedentary lifestyle to chemicals in the environment that affect sperm health.



Dr Sabanegh added he does not believe that doctors will start telling men with low sperm counts to wait until the winter or spring to try to conceive a child.



‘We would continue to encourage them to try regardless of the season, and they may benefit from interventions or treatments,’ he said.



The research comes just after new figures showed that nearly 20 per cent of couples spend more than a year trying for a baby.



It is also believed that eating a diet rich in saturated fats can lower sperm count in men

Experts have named women delaying motherhood and the obesity epidemic as the two most likely reasons for rising infertility.



There are now more mothers over 30 than at any time since records began - and further research has shown being overweight can interfere with ovulation in woman and sperm quality in men.



Further research published last month showed that young men who watch television for just three hours a day have half the sperm count of men rarely found in front of the box.



For the first time, the study showed falling sperm quality is linked to lower levels of physical activity.



Men who are mostly sedentary lose out to those who are moderately active, said the Harvard University study which was published in the British Journal of Sports Medicine.



Experts say the effect could be due to lack of exercise, or to overheating of the testicles caused by prolonged sitting.



It is also believed that eating a diet rich in saturated fats can lower sperm count in men.

Danish researchers found men who ate the most saturated fat had significantly lower sperm counts and poorer quality sperm than those who consumed the least.



