Daily broad-spectrum sunscreen use is an important intervention
to prevent squamous cell carcinoma and invasive
melanoma. Now dermatologists can feel confident confirming
that it prevents photoaging in middle aged adults as well. A
new randomized trial from Australia confirms that consistent
use of broad-spectrum sunscreen can slow photoaging in
adults in as little as four years in middle-aged adults. Because
young adults respond better to anti-aging messages than anti-cancer
messages regarding sun exposure, this data may help
motivate younger patients to avoid indoor tanning and pursue
consistent sun protection. Visual examples of aging over time
are particularly effective for teens and young adults.
Never Too Late: Daily Sunscreen Use Prevents Photoaging
Dermatologists promote sun safety, including daily sunscreen
and avoiding indoor tanning, to almost all patients.
While warnings about preventing future skin cancer can be
powerful, these warnings may seem too abstract to teens or
'too little too late' for older adults. Fortunately, avoiding ultraviolet
light can both prevent cancer and help people look
younger. New data about the efficacy of daily sunscreen to
prevent photoaging can be an important educational tool.
Combined with data from psychology literature, interventions
that highlight the risk of premature aging appear to
be more effective in changing behavior in teens and young
adults than warning about future cancer risks.
The role of consistent sunscreen use in preventing actinic
keratoses, squamous cell carcinoma, and invasive melanoma
has been established, particularly for high-risk populations
such as those with immunosuppression or history of previous
skin cancer.1,2 The extent to which sunscreen prevents
photoaging has been studied in mice and porcine models,
but only to a limited extent in humans. Limitations to human
studies on photoaging have been the relatively long observation
period that would be required to see differences, and
the need until now for pre- and post-study skin biopsies,
which are unappealing to potential study patients.
A new study published in June 2013 in the Annals of Internal
Medicine is the first to formally follow adult volunteers and
evaluate the impact of daily sunscreen use3. It was conducted
in Nambour, Australia near Brisbane at latitude 26 degrees south, comparable in latitude to Johannesburg, South Africa,
and north of the ozone hole that covers Antarctica. This
location is at the same latitude as southern Texas and Florida
in the northern hemisphere.
Six hundred white adults, mainly skin types I or II, age 25-55
were randomized to daily or discretionary sunscreen use. For
the group assigned to daily use, compliance was intermittently
monitored by weighing sunscreen tubes. For the group assigned
to discretionary use, by report all were using sunscreen
'frequently' and two-thirds reported regularly wearing hats
while outside before study onset. Each patient was assigned to
use the same broad-spectrum SPF 15 sunscreen with containing
octinoxate (Eusolex, or 8% ethylhexyl-p-methoxycinnamate)
that protects against ultraviolet B and 2% avobenzone (Parsol
1789, or 4-tert-butyl-4' methoxy-4-dibenzoylmethane) that protects
against a broad spectrum of ultraviolet A.
Photoaging was measured by analysis of skin texture and fine
wrinkling, so-called microtopography, of a silicone cast of the
skin at the beginning and end of the study period. This model has
shown to parallel elastin changes seen on skin biopsy and avoids
the more invasive skin biopsies that would otherwise be needed.
Among the 600 patients, those using daily sunscreen were
24% less likely to show any photoaging. A majority showed no
detectable increase in skin aging after 4.5 years, and some actually
showed an improvement in skin texture over baseline.
The protection from photoaging in the daily use group compared
to the discretionary group is even more striking because
the control group also used sunscreen and hats. These individuals
were instructed to continue to use sunscreen whenever
they thought it would be needed. This tells us that even in monitored
conditions, invidividuals may be poor judges of, or poor
planners for, conditions with excess UV radiation.
This study highlights that good news for patients seeing to prevent
photoaging:
This study was also powered to evaluate the efficacy of oral
beta carotene supplementation, at 30 mg daily, on photoaging,
and did not measure any significant difference from placebo.
