Hamburg - Older men trying to become fathers often discover that it's not as easily achieved as it is in youth.

Usually the man's entire lifestyle comes into question when fertility is impaired, said Hermann Behre of the university centre for reproductive medicine and andrology in Halle, Germany.

Smoking can have a negative effect on men advancing in age. Poor diet and lack of exercise also play a role. In addition, men who are overweight have a tendency toward diabetes and a reduction in the male hormone, said Behre.

Infertility in men can also be the first sign of a serious illness. Erectile dysfunction, for example, can indicate cardiovascular disease.

It's also a fact that lesser male infertility problems often do not regulate themselves in older men as well as they do in younger men. It is estimated that every sixth couple struggles with infertility problems.