Latitude, urbanization, age, and sex as risk factors for vitamin D deficiency disease in the Roman Empire.

The association of rickets with latitude may reflect care practices that, in more northerly locations where solar radiation is less intense, placed infants at increased risk of insufficient sunlight exposure to permit adequate vitamin D biosynthesis. The elevated level of vitamin D deficiency at Ostia may reflect, at least in part, the lack of sunlight due to dense occupation of multi-storey blocks that prevented direct sunlight from reaching living quarters and the streets between these closely spaced buildings.