Risk factors for IgA nephropathy: a case-control study with incident cases in Japan.

BACKGROUND/AIM: Our previous study with prevalent cases suggested that some genetic, immunological and lifestyle-related factors increased the risk of immunoglobulin A nephropathy (IgAN). To confirm this hypothesis, we conducted another case-control study.

METHODS

The study included 116 incident cases and 276 sex-, age- and residence-matched controls in central Japan. Information on family and individual history and on lifestyle was collected using a self-administered questionnaire. The strength of association between IgAN and a potential risk factor was assessed by calculating an odds ratio.

RESULTS

A family history of chronic glomerulonephritis, susceptibility to the common cold, episodes of tonsillitis in the preceding year, preference for salty foods and a high intake of rice and n-6 polyunsaturated fatty acids (PUFA) were associated with an increased risk of IgAN. Coffee consumption and dietary calcium intake were somewhat negatively related to the risk. A significance of alcohol drinking, use of vitamin supplements, consumption of raw eggs and intake of nutrients other than n-6 PUFA and calcium, though previously suggested, was not shown in the present study.

CONCLUSION

Our findings imply that some genetic factors, immune response to infections in the upper respiratory tract and nutritional imbalance would promote the development of IgAN.