OSLO 1986.

Methods	Open randomized trial conducted in ambulatory young male patients randomized to treatment or not in Norway.
Participants	785 patients with mean age 45.3 years, range 40 to 49 years. Ethnicity not reported. Baseline mean SBP/DBP was 156.2/97 mmHg and pulse pressure was 59 mmHg. Inclusion criteria: SBP 150 to 179 mmHg and DBP < 110 mmHg. Target < 140/90 mmHg. Exclusion criteria: New or previous coronary heart disease, cardiovascular disease, intermittent claudication, congestive heart failure or valvular heart disease, drug‐treated hypertension during the last year, diabetes mellitus (fasting blood sugar > 8.3 mmol/L), retinopathia (Keith‐Wagener grade 3 and 4), renal disease (proteinuria, hematuria, creatininc > 123.8 mmol/L, chronic nephritis), hepatic disease, psychosis, severe neurosis, persons regularly treated with psychopharmacologic drugs, malignant disease, and such chronic disease as rheumatoid arthritis, endocrine disorders, obvious alcohol abuse and social maladjustment, secondary hypertension, electrocardiographic changes at rest, left bundle branch block, atrial fibrillation, S‐T segment depressions Sl mm, marked left ventricular hypertrophy: R max + S max in precordial leads > 45 mm and simultaneous ST‐T changes (Minnesota code 4‐l, S‐T segment depression, and T‐wave flattening or inversion). Mean follow‐up: 5 years
Interventions	Treatment: hydrochlorothiazide (95%), methyldopa, and propranolol (26%). At 5‐year follow‐up, 36.7% were on HCTZ alone, 26% were on HCTZ + propanolol, 20% were on HCTZ + methyldopa, and 18% patients were on other drugs. Control group: no treatment
Outcomes	Stroke, CHD, mortality, CHF, systolic BP and diastolic BP
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "During 1973, 785 men, aged 40 to 49, with mild, symptom‐free hypertension were randomly assigned for a five‐year controlled drug treatment study, 406 men in the treatment group and 379 in the control group." "The randomization was performed by a random number table.” Comment: participants randomly allocated using random number tables and baseline characteristics were similar.
Allocation concealment (selection bias)	Low risk	The method used for allocation concealment was not mentioned. Participants and physician were aware of treatment given. Baseline characteristics were similar.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "Drug treatment was started with hydrochlorothiazide. If SBP remained above 140 mmHg, DBP above 90 mmHg, or both, alpha methyldopa was added. If there were side effects, methyldopa was replaced with propranolol. The control group was not given a placebo." Comment: no mention of blinding, both the participants and physicians were aware of the treatment provided.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Possible and definite coronary events and other cardiac complications were also evaluated by a “blind” diagnostic board of two independent cardiologists." Comment: blinding of the outcome assessor was probably done, though it was not clearly stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "In this study the patients have seen the same physicians and the same paramedical staff during 4 years and the drop‐out rate has been small, 0.6 per cent and the same in both groups." "Three men refused the drugs, and 13 (1.7%) dropped out of the study, three in the treatment group and 10 in the control group." "The mean observation time was 66 months (range: 60 to 76). Only 13 (1.7%) men failed to report for regular examinations. However, these men were followed for possible cardiovascular events at the end of the study." Comment: number of drop‐outs was low and patients were followed until end of study to account for all outcomes.
Selective reporting (reporting bias)	Low risk	Quote: “Each patient with cardiovascular events has been counted once, i.e., the number of events is identical with the number of patients with events. If a patient had more than one event, the most serious was counted. Nobody had both coronary heart disease and a cerebrovascular event”. Comment: all outcomes (coronary, cerebrovascular and other events) were properly reported and accounted for in the results section.
Other bias	Unclear risk	Conflict of interest was not reported. Source of funding was not stated.