27. Smoking ‐ Studies undertaking multivariable regression analyses to determine the effect of smoking 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 diabetes
WESDR Moss 1991	Prospective cohort	4	799	HbA1c, DM duration, DR severity at baseline, age, sex	OR	1.15	0.6 to 2.2		Ever vs never
WESDR Moss 1996	Prospective cohort	10	799	HbA1c, DM duration, DR severity at baseline, age, sex	OR	0.86a 0.94b	0.54 to 1.36 0.51 to 1.75
Grauslund 2009 (Thorlund)	Prospective cohort	5	573	HbA1c, DM duration, age, sex, SBP, DBP, comorbidities	OR	1.9a 0.87b	0.88 to 4.11 0.28 to 2.67
WESDR WESDR XVII	Prospective cohort	14	996	HbA1c, DR severity at baseline, BP, aspirin	OR	0.79	0.66 to 0.95	< 0.05	Diabetic pack years smoked per 10 years
Type 2 diabetes
Gui 2013	Retrospective cohort	2	205	DM duration, age, BP, C‐peptide	OR	1.07	1.04 to 1.11	< 0.05	% smokers vs non‐smokers
Nelson 1989	Prospective cohort	4	953	DM duration, age, sex	RR	0.70	0.2 to 1.9		Smoking: yes vs no
WESDR Moss 1991	Prospective cohort	4	1370	HbA1c, DM duration, DR severity at baseline	OR	1.13	0.45 to 7.83		Ever vs never
Gange 2021	Electronic database	5	71,817	HbA1c, age at DM diagnosis, race, comorbidities, income, insulin use	OR	0.84	0.7 to 1.0		Smoking
WESDR Moss 1996	Prospective cohort	10	1370	HbA1c, DM duration, DR severity at baseline	OR	Insulin 1.04b 1.15a Non‐insulin 0.8b 0.25a	0.49 to 2.22 0.47 to 2.8     0.23 to 2.8 0.03 to 2.06
Keen 2001	Prospective cohort	8	4483	DM duration, age, sex, SBP, DBP, co‐morbidities, insulin use, type of DM	OR	0.67		< 0.01	No vs yes

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

^aCurrent smoker
^bEx‐smoker