Antigenic stimulation and multiple myeloma. A prospective study.

BACKGROUND

A causal relationship between antigenic conditions and multiple myeloma was suggested by case reports. Although controlled studies identified associations with individual conditions, they failed to give overall support to the hypothesis. Using a prospective cohort representative of the U.S. population, the authors hypothesized that immune-stimulating conditions are a risk factor for multiple myeloma.

METHODS

The First National Health and Nutrition Examination Survey cohort of 14,407 persons were interviewed from 1971 to 1975 by the National Center for Health Statistics. Vital status with cause of death and hospitalizations were ascertained from 1982 to 1985 and in 1986. From the initial questionnaire, four risk factors were constructed: allergies (asthma, hives, hay fever, food allergies, and other allergies); autoimmune conditions (arthritis, thyroid disease and/or medication, rheumatic fever, diabetes, pernicious anemia); chronic bacterial conditions (chronic bronchitis or emphysema, chronic cough, tuberculosis, ulcers); and inflammatory conditions (gout, gallstones, recurrent or chronic enteritis, pleurisy).

RESULTS

Eighteen multiple myeloma (MM) cases were documented. The rate ratio (RR) of MM increased as the number of reported inflammatory conditions increased (one condition, RR = 2.0, 95% confidence interval [CI] = 1.2-3.3; 2 or more conditions, RR = 4.3, 95% CI = 1.5-12.4). The RR of myeloma also increased (P = 0.0002) with time since start of inflammatory conditions (RR = 1.6 for every 10 years of exposure). When cases were restricted to those with more than five years of follow-up, myeloma risk increased with the number of inflammatory conditions (two conditions, RR = 4.6, 95% CI = 1.5-13.8).

CONCLUSIONS

Although the number of cases is small and exposure may be misclassified, the prospective nature of the study design strengthens the results of the study.