Very low HDL cholesterol: The GSH Experience

Master Thesis

2022

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Background In epidemiological studies low HDL-C is associated with increased cardiovascular risk. In exceptional cases, e.g., patients with Apo A1 Milano, low levels of HDL-C are cardioprotective. Very little is known about the characteristics of South African patients with very low HDL-C. A detailed description of such a group will identify and characterize a cohort of patients for further study and help to identify clinical factors commonly associated with very low HDL-C in South Africa. Methods We retrospectively collected data on patients with HDL-C < 0.6 mmol/L attending a specialist lipid clinic at Groote Schuur Hospital (GSH) in Cape Town, South Africa. Eligible patients were identified by searching the GSH Lipid Clinic database and data was abstracted from their folders and entered into a Redcap database. Results One hundred and twenty eight (128) patient records were evaluated. The study cohort was predominantly male (60%). The mean (SD) age at presentation was 44.6(11.4) years with males and females presenting at similar ages (p=0.474). Most patients were white followed by mixed ancestry and black African patients. The mean (SD) total cholesterol for the cohort was 8.47(5.13) mmol/L. The mean (SD) HDL-C was 0.53(0.10) mmol/L, while the mean (SD) LDL-C was 4.86(2.10) mmol/L. The median (IQR) triglycerides was 6.05(3.1 – 11.50) mmol/L. Baseline lipid profile showed that very low HDL-C was associated with elevated total cholesterol and hypertriglyceridemia in many patients. 8.59% of the cohort had very low HDL-C levels with normal levels of triglycerides. On follow-up, the best HDL-C ranged from 0.5 – 1.8mmol/L, while the worst recorded HDL-C ranged from 0.2-1.0mmol/L. There was no relationship between age of presentation and level of HDL-C. Hypertension was highly prevalent (39.74% of males and 42% of females). Diabetes was also highly prevalent (41.02% of males and 30.0% of females). At presentation 19.23% males reported a previous cardiovascular complication such as stroke or myocardial infarction compared to 10.00% of the females. Participants that had “Never Smoked” had the lowest HDL-C levels. There was no statistically significant difference in levels of HDL-C at presentation in the patients who were consuming alcohol compared to those who were not consuming alcohol (p=0.7406) Conclusion This study has provided important insights into the characteristics of patients with very low HDL-C in Cape Town South Africa. As expected, it confirms the relationship between low HDLC and the metabolic syndrome as well as the use of medications known to lower HDL-C (beta blockers). The inverse correlation between high triglycerides and low HDL-C was also demonstrated. Unexpected was that HDL-C was not found to correlate with smoking (which tends to lower HDL-C) or alcohol use (which tends to raise HDL-C). Early initiation of lipidmodifying therapy should be encouraged given the high prevalence of other cardiovascular risk factors, or established atherosclerotic cardiovascular disease, in these patients. Patients with very low HDL-C, but without hypertriglyceridaemia would be a worthwhile cohort to study to characterize genetic determinant of very low HDL-C in South Africa.
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