The research, which collated and reviewed data from 90 previous studies, found consistent age-related declines in semen volume and sperm performance.
The study also noted increases in malformed and DNA-damaged sperm, also likely reflecting a decline in male fertility.
Study lead author Dr Sheri Johnson said the Otago researchers were proud of the study, which was based on a systematic review of the scientific literature and an overall ''meta-analysis'' of the respective studies' data.
The work, which began about three years ago, had been undertaken by researchers from the university's departments of zoology and anatomy.
This was the biggest quantitative meta-analysis of studies on male sperm quality, from more than 30 countries, and involving about 94,000 volunteers/patients, she said.
Understanding how age affected fertility was becoming increasingly important as couples delayed childbearing toward later stages of their lives, Dr Johnson said.
While female age was well known to have negative effects on fertility, reproductive success and health of offspring, the influence of male age on a couple's fertility had been ''largely neglected''.
The effects of declining semen traits with increasing male age had previously been largely ignored, because of ''inconsistencies in the literature'', but the Otago study now showed that male age affected a variety of sperm characteristics.
It was well recognised that reduced sperm performance could affect pregnancy success, but it was less well known that the quality of the sperm, particularly DNA quality, could affect the development and health of the offspring, she said.
Their Marsden-funded study appeared in the international journal, Ageing Research Reviews.
Prof Neil Gemmell, a study co-author, says the research findings suggested that further awareness of the potential consequences of male age on reproductive outcomes was needed.
Older fathers
• Peter Bromhead MNZM, who has been married three times, became perhaps New Zealand's oldest ''new'' father in October 2011, at age 78, when his third wife, Carolyn Bromhead, in her mid-30s, gave birth to a boy.
• And one of the country's longest-serving mayors, Tim Shadbolt, then 65, became a father for the fourth time, in mid-2012, after his partner, Asha Dutt, also gave birth to a son.
