Seasonal onset of insulin dependent diabetes in relation to sex and age at onset.

All newly diagnosed insulin dependent diabetics presenting consecutively to the Diabetic Department of the Royal Infirmary from the City of Edinburgh or its environs, between the years 1964 and 1977, were analysed for sex (297 males, 205 females), age at diagnosis (range 10--75 years), month of diagnosis, duration of symptoms and month of symptomatic onset. Males aged 10--19 years showed a significant seasonal variation in diagnosis (p less than 0.025) with an increase in autumn and winter months which was not seen in females aged 10--19 years nor in patients of either sex aged more than 19 years at diagnosis. The duration of diabetic symptoms increased with increasing age at diagnosis in both males and females and was consistently greater in females than in males for each age group at diagnosis. When the month of symptomatic onset was considered in relation to sex and age at diagnosis, having excluded patients with duration of symptoms of more than three months, only males aged 10--19 years at diagnosis showed a significant seasonal variation in incidence (p less than 0.005).