BACKGROUND

Sunscreen use and dietary antioxidants are advocated as preventives of skin aging, but supporting evidence is lacking.

OBJECTIVE

To determine whether regular use of sunscreen compared with discretionary use or β-carotene supplements compared with placebo retard skin aging, measured by degree of photoaging.

DESIGN

Randomized, controlled, community-based intervention. (Australian New Zealand Clinical Trials Registry: ACTRN12610000086066).

SETTING

Nambour, Australia (latitude 26° S).

PATIENTS

903 adults younger than 55 years out of 1621 adults randomly selected from a community register.

INTERVENTION

Random assignment into 4 groups: daily use of broad-spectrum sunscreen and 30 mg of β-carotene, daily use of sunscreen and placebo, discretionary use of sunscreen and 30 mg of β-carotene, and discretionary use of sunscreen and placebo.

MEASUREMENTS

Change in microtopography between 1992 and 1996 in the sunscreen and β-carotene groups compared with controls, graded by assessors blinded to treatment allocation.

RESULTS

The daily sunscreen group showed no detectable increase in skin aging after 4.5 years. Skin aging from baseline to the end of the trial was 24% less in the daily sunscreen group than in the discretionary sunscreen group (relative odds, 0.76 [95% CI, 0.59 to 0.98]). β-Carotene supplementation had no overall effect on skin aging, although contrasting associations were seen in subgroups with different severity of aging at baseline.

LIMITATION

Some outcome data were missing, and power to detect moderate treatment effects was modest.

CONCLUSION

Regular sunscreen use retards skin aging in healthy, middle-aged men and women. No overall effect of β-carotene on skin aging was identified, and further study is required to definitively exclude potential benefit or potential harm.

PRIMARY FUNDING SOURCE

National Health and Medical Research Council of Australia.