Oxford Retinopathy 1978.

Study characteristics
Methods	RCT Summary risk of bias: moderate to high for CVD outcomes, low for all‐cause mortality
Participants	Newly‐diagnosed non‐insulin‐dependent diabetics (UK) CVD risk: moderate Control: number randomised unclear (249 split between the 2 groups, 125?), number analysed for mortality unclear (all but 2 overall at 16 years) Intervention: number randomised unclear (249 split between the 2 groups, 125?), number analysed as above Mean years in trial: overall 9.3? % male: overall 49% Age: mean overall 47.1 (all < 65) Ethnicity: not stated Statins use allowed? Unclear % taking statins: Not reported (probably none as too early, pre‐1980)
Interventions	Reduced and modified dietary fat vs average diet Control aims: total fat 40%E, PUFA 12%E, protein 20%E, CHO 40%E (reducing simple sugars), 1500 kcal/day Intervention aims: total fat 26%E, PUFA 16%E, protein 20%E, CHO 54%E (reducing simple sugars), 1500 kcal/day Control methods: dietary advice from diabetes dietitian Intervention methods: dietary advice from diabetes dietitian Total fat intake, %E (at 7 ‐ 9 years)§: int 32 (SD unclear), cont 41 (SD unclear) (mean difference ‐9.00, 95% CI ‐11.48 to ‐6.52 assuming SDs of 10) significant reduction Saturated fat intake, %E (at 7 ‐ 9 years)§: int 10.7 (SD unclear), cont 20.4 (SD unclear) (mean difference ‐9.70, 95% CI ‐10.94 to ‐8.46 assuming SD of 5) significant reduction PUFA intake, %E (at 7 ‐ 9 years)§: int 11.8 (SD unclear), cont 2.1 (SD unclear) (mean difference 9.70, 95% CI 8.46 to 10.94 assuming SDs of 5) significant increase PUFA n‐3 intake: not reported PUFA n‐6 intake: not reported MUFA intake, %E (at 7 ‐ 9 years)§: int 9.5 (SD unclear), cont 18.6 (SD unclear) (mean difference ‐9.10, 95% CI ‐10.34 to 7.86 assuming SDs of 5) significant reduction Carbohydrate intake: not reported Protein intake: not reported Trans fat intake: not reported Replacement for saturated fat: PUFA and CHO (based on dietary goals and achievements) Style: diet advice Setting: community (outpatients clinic) §validity of these data is questionable as it represents only 3 intervention and 3 control participants. Source: Lopez‐Espinoza 1984
Outcomes	Stated trial outcomes: retinopathy Data available on total mortality? yes, but unable to ascertain from which intervention groups (34 deaths at 10 years) Cardiovascular mortality? no Events available for combined cardiovascular events: none Secondary outcomes: none Tertiary outcomes: BMI, total cholesterol
Notes	Study duration over 9 years Study aim was to reduce total fat and increase PUFAs (so reducing saturates), and saturated fat intake in the intervention group was significantly lower than in the control group SFA reduction achieved Total serum cholesterol, difference between intervention and control, mmol/L: 0.07 (95% CI ‐0.34 to 0.48), NO statistically significant reduction and smaller than 0.20 Trial dates: Recruitment 1973 to 1976 Funding: Oxford Diabetes Trust, British Diabetic Association, International Sugar Research Foundation Inc Declarations of Interest of primary researchers: none stated, all authors worked for academic or health institutions.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"random number sequence, provided and allotted by a separate agency" (Prof Richard Peto)
Allocation concealment (selection bias)	Low risk	"random number sequence, provided and allotted by a separate agency" (Prof Richard Peto)
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants were not blinded.
Blinding of outcome assessment (detection bias) CVD outcomes	Unclear risk	Unclear whether physicians blinded to allocation
Blinding of outcome assessment (detection bias) All‐cause mortality	Low risk	Blinding is not relevant in assessment of mortality.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear, deaths, cancer and CV events are dropouts ‐ unclear if any data missing
Selective reporting (reporting bias)	Low risk	Not relevant for primary and secondary outcomes as all trialists were asked for data
Free of systematic difference in care?	Low risk	Dietetic advice for both groups. See control and intervention methods in the Interventions section of the table of Characteristics of included studies
Stated aim to reduce SFA	High risk	Aim to reduce SFA not stated
Achieved SFA reduction	Low risk	SFA reduction achieved
Achieved TC reduction	High risk	No statistically significant TC fall, and difference only 0.07 mmol/L
Other bias	Low risk	None noted