Sunscreen plays a much more important role than just protecting against sunburn

Jul 12 2005

The number of nevi, or moles, a person has is known to be a strong predictor of the future risk of developing skin cancer, particularly melanoma, the most deadly form of the disease. This number also is believed to be affected by the amount of sun exposure an individual receives.

Since most people receive a great deal of sun exposure in their youth, children with many nevi may be at greatest risk for developing melanoma as an adult. Dermatologists are now looking at sunscreen usage in children as a potential tool to help curtail the development of nevi and thereby reduce the chance of skin cancer in the future.

"Sunscreen has always been an important part of an overall sun-safety regime to protect the skin and reduce the number of sunburns, especially for children," said dermatologist Jason K. Rivers, M.D., professor of dermatology, Department of Medicine, University of British Columbia, and co-author of a study published in the April 2005 issue of the Journal of the American Academy of Dermatology. "This study demonstrates that sunscreen plays a much more important role than just protecting against sunburn. By preventing nevi development, sunscreen decreases the risk of developing skin cancer in the future."

The study included 309 Caucasian schoolchildren - first-graders, ages 6 to 7 years old, and fourth-graders, ages 9 to 10 years old - who were monitored for three years. Prior to the start of the study, each child was examined by a physician who counted the number of moles at least 2 mm or larger on specific sites of the body, including the head and neck, trunk, upper limbs and lower limbs. The degree of freckling on the face, arms and shoulders also was noted using a standardized freckling chart that compares the coverage and density of freckles.

The children were randomized into two groups - the parents of one group received two bottles of sun protection factor (SPF) 30 broad-spectrum sunscreen annually with instructions to use it on all sun-exposed skin whenever the child was expected to be in the sun for 30 minutes or more; and the parents of the second group received no sunscreen and no advice on sunscreen use. Parents in both groups received follow-up questionnaires twice a year to assess the children's outdoor activities, clothing preferences and sunscreen use during the activities.

After three years, each child was re-examined to determine the median number of new nevi and the amount of freckling. It was determined that of the group who received sunscreen and instructions for usage, the number of new nevi was less, particularly on the trunk and upper and lower limbs.

"Not only did the children in the sunscreen group develop less nevi, it is of some significance that there was a reduction in the number of new nevi on areas of the body which do not receive regular sun exposure," said Dr. Rivers. "Since melanoma can develop anywhere on the body, including on areas that are not exposed to the sun, these results may indicate that sunscreen usage has an overall positive affect on all parts of the body, thereby reducing the risk of skin cancer."

For children with freckles in both groups, the control group saw an increase in the number of nevi on the trunk, while the sunscreen group saw little or no increase. "The use of sunscreen to prevent new nevi development in these children is particularly important, because children with freckles often have lighter skin, hair and eye color and coupled with numerous nevi, they are already at increased risk for future skin cancer," stated Dr. Rivers.

When broken down by age, the effect of sunscreen on nevi development was more obvious for the fourth-grade students than the first-grade students. "Age may play a significant factor in the emergence of new nevi, since children develop an increasing number of nevi as they progress through childhood to adolescence," said Dr. Rivers.

Another benefit of the study is that the children in the sunscreen group learned about the importance of using sunscreen correctly to protect their skin. "The directions for using sunscreen may have played a part in the positive results since previous studies have shown that most people do not use sunscreen correctly, frequently applying only 20 to 50 percent of the recommended amount of sunscreen," said Dr. Rivers. "By educating parents, we're hopeful that these children have developed a lifelong habit of applying sunscreen whenever they are headed outdoors which will continue to greatly reduce their risk of developing skin cancer as adults."