15. High‐density lipoprotein (HDL) ‐ Studies undertaking multivariable regression analyses to determine the effect of HDL on progression to PDR.

Study	Study type	Time years	N at baseline	Adjustment factors	Effect estimate			P value	Comments
					Type	Value	95% CI
Type 1
Porta 2001	Prospective cohort	7	2013	HbA1c, DM duration				Reported narratively as nonsignificant
Type 2 diabetes
Lee 2021	Retrospective cohort	6	2623	HbA1c, DR severity at baseline, age, sex, BMI	HR	0.88	0.76 to 1.01	0.07	Per one standard deviation

BMI: body mass index; CI: confidence interval; DBP: diastolic blood pressure; DM: diabetes mellitus; DR: diabetic retinopathy; HbA1c: glycated haemoglobin/haemoglobin A1c; HR: hazard ratio; NPDR: non‐proliferative diabetic retinopathy; OR: odds ratio; PDR: proliferative diabetic retinopathy; RR: risk ratio; SBP: systolic blood pressure; vs: versus