Ambulatory blood pressure monitoring phenotypes and circadian blood pressure patterns among adults referred for diagnostic evaluation at Aga Khan University Hospital, Nairobi, Kenya: a retrospective cross-sectional study

Introduction: hypertension represents the primary modifiable risk factor for cardiovascular disease and poses a public health challenge in sub-Saharan regions, with Kenya experiencing particularly low detection and control rates. Traditional office-based blood pressure measurements often fail to detect key phenotypes, such as white-coat and masked hypertension. Ambulatory Blood Pressure Monitoring (ABPM) offers a comprehensive 24-hour profile that excludes white-coat hypertension and allows for the evaluation of circadian patterns, including nocturnal hypertension and non-dipping status, both of which are recognized as high-risk phenotypes strongly linked to adverse cardiovascular events. This study evaluated ABPM data from Aga Khan University Hospital, Nairobi (AKUHN), to characterize these high-risk phenotypes and identify associated factors. Methods: we performed a retrospective cross-sectional analysis at Aga Khan University Hospital in Nairobi, spanning from January 2022 to June 2024. Adults (≥18 years) referred for ABPM for diagnostic clarification were included, excluding those with treated hypertension. Data on demographics, cardiovascular risk factors, and ABPM parameters (24-hour, daytime, nighttime pressures, and dipping status) were collected. Hypertension and circadian patterns were classified according to the 2017 AHA/ACC criteria. Results were summarized as frequencies, proportions, and means. Group comparisons used chi-squared/Fisher´s exact tests for categorical and student´s t-test for continuous variables. Multivariate logistic regression identified predictors of adverse circadian patterns (non-dipping and reverse dipping). Statistical significance was set at p<0.05. Results: a total of 180 patients were included in the analysis, with a median age of 47 years (IQR 38-62); 124 (68.9%) were aged >40 years. Males accounted for 95 (52.8%) of the cohort, and 78 (46.2%) were diabetic. The mean office systolic and diastolic pressures were 143.1 ± 20.1 mmHg and 82.4 ± 12.5 mmHg, respectively. Using ABPM, hypertension was confirmed in 171 (95.0%) patients. Nocturnal hypertension was more prevalent than daytime hypertension (152, 84.4% vs. 128, 71.1%). Circadian patterns showed that 139 (77.2%) exhibited a non-dipping or reverse-dipping status. Reverse dippers had the highest mean nocturnal systolic/diastolic pressures (142.3 ± 15.5 / 83.7 ± 11.1 mmHg). No factors demonstrated a statistically significant (P-value <.05) association with adverse circadian rhythm patterns. However, individuals with higher BMI and those with diabetes showed a trend toward increased odds of adverse circadian rhythm. Conclusion: this study revealed a high prevalence of hypertension, particularly nocturnal hypertension, with most patients showing non-dipping patterns linked to greater cardiovascular risk. Although no factors were significantly associated with adverse circadian rhythms, patients with higher BMI and diabetes demonstrated increased odds, highlighting the high-risk phenotypes.