Body weight may play a role in maintaining health sperm counts with age, according to new study. File photo by Sebastian Kaulitzki/Shutterstock
May 2 (UPI) -- Overweight older men experience more negative age-related changes to their sperm cells than those who maintain a healthy weight, a study published Monday found.
These changes mean their sperm cells are less robust, which may result in lower sperm counts and infertility, the researchers said in an article published Monday by the journal Developmental Cell.
Older men with a body mass index -- a measure of weight against height -- above 30 showed a very limited ability to develop sperm cells, the data showed.
Older men with BMIs below 27, however, displayed an ability to produce sperm cells with few molecular changes that differentiated them from samples collected from younger study participants, according to the researchers.
"Aging may confer a combination of modest molecular changes that sensitize the testis for additional dysregulation," study co-author Bradley Cairns said in a press release.
"Pronounced dysregulation [is] caused when aging is combined with additional factors such as obesity," said Cairns, a professor of oncological sciences at the University of Utah School of Medicine in Salt Lake City.
BMI is calculated by taking a person's weight and dividing it by their height in square meters, according to the Centers for Disease Control and Prevention.
People with BMIs of about 19 to 25 are considered normal weight, while those with BMIs of 25 to 30 are considered overweight, the agency says.
A BMI of 30 of above means a person is obese, the CDC says, noting that about 40% of adults in the United States meet the criteria for obesity.
Most studies have found that male sperm count peaks at about age 17 and begins to decline at age 40.
Sperm counts decline with age, even with procedures such as in vitro fertilization, according to a recent study.
For this research, Cairns and his colleagues used genetic sequencing to profile more than 44,000 cells obtained from autopsy testicular samples from four young men, ages 17 to 22, and eight older men, 60 years old and older.
The older donors were screened for having offspring as young adults to ensure early-adult fertility, the researchers said.
The young samples clustered together and did not display molecular signatures of aging or a disrupted ability to produce sperm cells," the data showed.
The older samples showed only modest age-related changes in stem cells that give rise to mature sperm, according to the researchers.
However, age-related changes, including lower sperm counts, were more prominent in men who met the criteria for obesity, they said.
The results reveal that the molecular mechanisms underlying the complex testicular changes associated with aging may be worsened by chronic conditions such as obesity, the researchers said.
Larger studies are needed to confirm the results and to identify potential roles for diet, exercise, diabetes or altered hormone production in the aging of sperm cells, according to the researchers.
"Our study reveals potential biomarkers for diagnosis of testis aging and directions for potential treatment of aging-related subfertility," study co-author Jingtao Guo said in the press release.
"It also serves as a foundational dataset for the scientific community to study how human testis and fertility respond to aging," said Guo, an assistant professor of surgery at the University of Utah.