Non-Hodgkin's lymphoma the cancer that killed Jackie Kennedy Onassis has been linked to ultraviolet light, used by sunbeds and for treating psoriasis and other skin diseases.

The disease has reached epidemic proportions around the world. Cases have been rising by up to 4 per cent a year over the last few years in Sweden and Denmark alone, where recent research has been carried out.

The rise has coincided with increases of HIV cases, but not all cases could be attributed to the infection, even though this appeared to be only one of the few variables in the last decade.

Indeed, records have shown that just 27 per cent of cases of non-Hodgkin's lymphoma in the US were linked with HIV in 1992. Other causes include rheumatoid arthritis and a history of blood transfusions, but even these do not account for the epidemic.

Because there is a close link between non-Hodgkin's lymphoma and skin cancer, scientists suspect that ultraviolet light long associated with skin cancer for its immunosuppressing qualities might also be responsible for causing lymphoma.

Researchers from University Hospital in Uppsala, Sweden, studied the reports of 115,000 patients who had various skin cancers and lymphoma.

Those with skin cancers were used as "markers" for exposure to ultraviolet light, and researchers looked at the association with the development of non-Hodgkin's lymphoma.

They discovered that the risk of non-Hodgkin's lymphoma increased two-fold if skin cancer had already been diagnosed. By implication, they were able to suggest a link between the lymphoma and ultraviolet light (BMJ, June 10, 1995).