
                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, July 5, 1990                   TAG: 9007050071
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A-10   EDITION: METRO 
SOURCE: The New York Times
DATELINE:                                 LENGTH: Medium

SEASON AFFECTS FERTILITY

Men who live in temperate climates produce significantly fewer sperm in summer than in winter, researchers report, a finding that partly accounts for fewer births in the spring.

Scientists have long been puzzled by lower spring birth rates. Previous studies have found that there is no significant decrease in sexual intercourse during the summer.

While sperm counts are lower in the summer, and high temperatures are known to interfere with sperm production, heat alone is not the explanation, the researchers said.

The decline affects even men who work in air-conditioning. The diminished fertility may be related more to exposure to daylight, an accompanying editorial suggested in calling for more research.

The new study, led by Richard J. Levine, an epidemiologist at the Chemical Industry Institute of Toxicology at Research Triangle Park, N.C., is reported in the current issue of The New England Journal of Medicine.

The researchers analyzed semen samples donated in summer and winter by 131 men who worked outdoors an average of eight hours a day in San Antonio. They found that both the density and the number of sperm were a quarter to a third lower in summer than in winter. In the winter the mean total of sperm per ejaculation was 319.4 million and in the summer the mean was 244.9 million.

After ruling out length of sexual abstinence, cigarette smoking, disease and drug use as causes, the group found that only the season could be linked with the reduced amount of sperm. The researchers also found no correlation between lower sperm counts and working without air-conditioning.

Since a similar decline in fertility has been found in men who live in France and Switzerland, where the summers are cooler, heat alone cannot entirely explain the results, the researchers said.

An editorial accompanying the paper said exposure to daylight might be a more likely explanation and deserved more study. Further carefully controlled clinical studies are needed to determine the factors that affect sperm production so that doctors can better treat men with fertility problems, the editorial said.

by CNB