Effect of Ramadan Fasting on Blood Pressure and Kidney Functions in Newly Diagnosed Hypertensive Patients: A Study in Konya, Turkey

Dear Editor,

We sincerely thank Dr. Kalcik and colleagues for their thoughtful comments on our article, “Effect of Ramadan Fasting on Blood Pressure and Kidney Functions in Newly Diagnosed Hypertensive Patients: A Study in Konya, Turkey.” In that retrospective, single-center study of newly diagnosed hypertensive adults uniformly initiated on an ACEI/ARB plus hydrochlorothiazide regimen, we examined short-term (1-month) blood pressure trajectories and renal safety during Ramadan [1]. We are encouraged that our findings—similar to end-of-month blood pressures between fasting and non-fasting groups and no deterioration in creatinine or eGFR—have prompted constructive discussion. Many of the methodological considerations raised in the letter were acknowledged in our article, and we appreciate the opportunity to expand on them in this response.

We agree that a retrospective, single-center design limits causal inference and generalizability. As noted in our Limitations, this was a hypothesis-generating study in which we deliberately used a uniform ACEI/ARB + hydrochlorothiazide regimen to minimize treatment heterogeneity and better isolate the effect of fasting [1]. The logical next step is a prospective, multicenter investigation across diverse antihypertensive classes and populations.

Regarding therapy class, we intentionally restricted treatment to an ACEI/ARB plus low‑dose hydrochlorothiazide to minimize pharmacologic heterogeneity and because contemporary guidelines endorse initial two‑drug combinations pairing a renin–angiotensin system blocker with either a calcium‑channel blocker or a thiazide/thiazide‑like diuretic [2]. In the Ramadan context of anticipated daytime hypohydration, this design allowed us to pragmatically assess whether the thiazide component would precipitate volume‑related adverse effects or metabolic/electrolyte derangements; in our cohort, we observed neither clinically meaningful electrolyte shifts nor renal deterioration at 1 month. Prior evidence likewise suggests that diuretic‑based regimens can be well tolerated during Ramadan with appropriate monitoring [3]. We agree that regimen‑specific effects warrant confirmation in prospective multicenter studies that also include CCB‑based combinations.

We agree that dietary sodium and hydration are key confounders [4]. As explicitly noted in our Limitations (p. 5), the retrospective design precluded reliable quantification of sodium/sugar and daily fluid intake; neither structured food-frequency questionnaires nor biochemical markers such as 24-h urinary sodium were collected [1]. Accordingly, we proposed that prospective studies incorporate standardized FFQs and objective measures (e.g., 24-h urinary sodium) to better isolate the independent effect of Ramadan fasting on BP and renal outcomes.

We fully agree and consider this the most important shortcoming of our study that unmeasured sleep and circadian disruption during Ramadan could confound BP trajectories. As we noted in the Discussion (p. 3), sleep patterns can influence BP variability, but we did not quantify sleep in this retrospective analysis [1]. Ramadan is associated with delayed bedtimes, shorter total sleep time, altered sleep architecture (notably reduced REM), and increased daytime sleepiness changes that can shift autonomic balance and BP rhythms [5]. Sleep irregularity itself is linked to blunted nocturnal dipping and greater BP variability, which relate to adverse cardiovascular risk [6]. Accordingly, future protocols should incorporate validated sleep assessments (e.g., PSQI, Epworth), actigraphy, and time‑stamped ambulatory BP monitoring to integrate nocturnal BP/dipping status with sleep timing and quality [7].

We agree that longer follow‑up is essential. In our cohort, 1‑month assessments showed no renal deterioration (stable creatinine/eGFR) and similar end‑of‑month blood pressures between fasting and non‑fasting patients—findings detailed in Tables 2–4—which are reassuring in the short term but cannot address potential cumulative effects from repeated annual fasting. Accordingly, as outlined in our Limitations and Conclusion, we advocate multi‑year, multicenter cohorts to track long‑term renal and cardiovascular trajectories across therapy regimens.

We thank Dr. Kalcik and colleagues for their constructive insights and the opportunity to clarify points of agreement. In line with their comments—and as reflected in our data—we believe our findings offer short-term reassurance under clinical supervision for newly diagnosed hypertensives treated with a diuretic-containing ACEI/ARB regimen, while we fully endorse multicenter, regimen-diverse, longer prospective studies to define long-term outcomes.

All authors contributed to the planning, writing, and revision.

The authors have nothing to report.

The authors declare no conflicts of interest.