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Risk factors for IgA nephropathy: a case-control study with incident cases in Japan
Kenji Wakai1, Shigeru Nakai, Seiichi Matsuo
1Department of Preventive Medicine/Biostatistics and Medical Decision Making, Nagoya University Graduate School of Medicine, Nagoya, Japan. wakai@med.nagoya-u.ac.jp
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.