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      We thank Dr. Kawada for his interest in our study on effects of coffee intake on incident chronic kidney disease.
      • Jhee JH
      • Nam KH
      • An SY
      • et al.
      Effects of Coffee Intake on Incident Chronic Kidney Disease: A Community-Based Prospective Cohort Study.
      Kawada gave us two thoughtful comments.
      First, we did not observe dose-response relationship between coffee intake and risk of incident CKD in our study. There has been evidence that coffee intake is inversely associated with diabetes, dementia, and hypertension in a dose-dependent manner.
      • O'Keefe JH
      • Bhatti SK
      • Patil HR
      • DiNicolantonio JJ
      • Lucan SC
      • Lavie CJ
      Effects of habitual coffee consumption on cardiometabolic disease, cardiovascular health, and all-cause mortality.
      • Xie C
      • Cui L
      • Zhu J
      • Wang K
      • Sun N
      • Sun C
      Coffee consumption and risk of hypertension: a systematic review and dose-response meta-analysis of cohort studies.
      However, our observational study could not estimate accurate amount of coffee intake, which led us to analyze the data with frequency of coffee intake alone. In addition, potential confounding factors that could affect the outcomes might not be captured by our database. Notably, there were more smokers and alcohol drinkers in coffee consumers with ≥ 2 cups/day. We also found that smoking and alcohol binge drinking had a harmful impact on kidney disease progression (manuscripts in preparation). We assume that these unfavorable factors might mitigate the benefits of higher levels of coffee intake on CKD development.
      • Ricardo AC
      • Anderson CA
      • Yang W
      • et al.
      Healthy lifestyle and risk of kidney disease progression, atherosclerotic events, and death in CKD: findings from the Chronic Renal Insufficiency Cohort (CRIC) Study.
      • Michishita R
      • Matsuda T
      • Kawakami S
      • et al.
      The Association Between Unhealthy Lifestyle Behaviors and the Prevalence of Chronic Kidney Disease (CKD) in Middle-Aged and Older Men.
      Given great interest in the effects of coffee on health among the general population, future studies should focus on the dose-response relationship between coffee intake and incident chronic kidney disease.
      Second, we agree with Kawada's opinion on the possible effect of smoking on chronic kidney disease. There have been a number of studies showing that active cigarette smoke is associated with an increased risk for chronic kidney disease.
      • Yoon HJ
      • Park M
      • Yoon H
      • Son KY
      • Cho B
      • Kim S
      The differential effect of cigarette smoking on glomerular filtration rate and proteinuria in an apparently healthy population.
      • Xia J
      • Wang L
      • Ma Z
      • et al.
      Cigarette smoking and chronic kidney disease in the general population: a systematic review and meta-analysis of prospective cohort studies.
      As aforementioned, although we did not present the relevant data in the published article,
      • Jhee JH
      • Nam KH
      • An SY
      • et al.
      Effects of Coffee Intake on Incident Chronic Kidney Disease: A Community-Based Prospective Cohort Study.
      we found that smoking had a negative influence on chronic kidney disease in our study: Smokers (current or former) had a 20% increased risk of incident chronic kidney disease (HR, 1.21; 95% CI, 1.03-1.423). We also adjusted proteinuria by dipstick urine test, but the study did not quantitatively measure albuminuria. Nevertheless, smoking- and proteinuria-adjusted Cox model did not change the main results. Unfortunately, the database did not include the exact amount of smoking, thus cigarette dose-response relationship could not be evaluated. As Kawada commented, smoking-related kidney problems are important and our ongoing in-depth analyses using the database from Korean chronic kidney disease cohort
      • Oh KH
      • Park SK
      • Park HC
      • et al.
      KNOW-CKD (KoreaN cohort study for Outcome in patients With Chronic Kidney Disease): design and methods.
      will be able to clarify this association.

      References

        • Jhee JH
        • Nam KH
        • An SY
        • et al.
        Effects of Coffee Intake on Incident Chronic Kidney Disease: A Community-Based Prospective Cohort Study.
        Am J Med. 2018; 131: 1482-1490.e3https://doi.org/10.1016/j.amjmed.2018.05.021
        • O'Keefe JH
        • Bhatti SK
        • Patil HR
        • DiNicolantonio JJ
        • Lucan SC
        • Lavie CJ
        Effects of habitual coffee consumption on cardiometabolic disease, cardiovascular health, and all-cause mortality.
        J Am Coll Cardiol. 2013; 62: 1043-1051
        • Xie C
        • Cui L
        • Zhu J
        • Wang K
        • Sun N
        • Sun C
        Coffee consumption and risk of hypertension: a systematic review and dose-response meta-analysis of cohort studies.
        J Hum Hypertens. 2018; 32: 83-93
        • Ricardo AC
        • Anderson CA
        • Yang W
        • et al.
        Healthy lifestyle and risk of kidney disease progression, atherosclerotic events, and death in CKD: findings from the Chronic Renal Insufficiency Cohort (CRIC) Study.
        Am J Kidney Dis. 2015; 65: 412-424
        • Michishita R
        • Matsuda T
        • Kawakami S
        • et al.
        The Association Between Unhealthy Lifestyle Behaviors and the Prevalence of Chronic Kidney Disease (CKD) in Middle-Aged and Older Men.
        J Epidemiol. 2016; 26: 378-385
        • Yoon HJ
        • Park M
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        • Son KY
        • Cho B
        • Kim S
        The differential effect of cigarette smoking on glomerular filtration rate and proteinuria in an apparently healthy population.
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        • Wang L
        • Ma Z
        • et al.
        Cigarette smoking and chronic kidney disease in the general population: a systematic review and meta-analysis of prospective cohort studies.
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        • Oh KH
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        KNOW-CKD (KoreaN cohort study for Outcome in patients With Chronic Kidney Disease): design and methods.
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