To the Editor: In their study of the relationship between diurnal blood pressure and congestive heart failure (CHF), Dr Ingelsson and colleagues1 used 5 models to adjust for several covariates, including use of antihypertensive medications, prior myocardial infarction, diabetes, smoking, body mass index, and serum cholesterol level. However, we are concerned that the results of the study may have been confounded by chronic kidney disease (CKD). No measures of kidney function were provided to estimate glomerular filtration rate (GFR) of the study participants. While the incidence of CKD is not known for the Swedish population or in this middle-aged cohort, of whom 50% had hypertension, 10% had diabetes, and in whom overall body mass index was elevated, it is likely that at least 10% possessed moderate CKD (GFR<60 mL/min per 1.73 m2).2 It is also likely that approximately 50% had mild CKD (GFR 60-89 mL/min per 1.73 m2).2
Chronic kidney disease could serve as a major confounding variable in this study because it is causally related to both the exposure and the outcome. Decrements in GFR are linked to alterations in diurnal blood pressure regulation. For example, nocturnal dipping is lost within a week of kidney donation,3 is absent in the majority of patients with mild to moderate stages of CKD,4 is inversely correlated with GFR,5 and is restored with kidney transplantation.6 CKD is a major risk factor for the development of CHF. Therefore, the lack of measurement and adjustment for baseline renal function in this cohort should be noted as a limitation of this study.
Financial Disclosures: None reported.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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