Digiesi 1990.

Methods	Randomized, placebo‐controlled, cross‐over trial. 2 week washout period, 10 week treatment period, 2 week treatment suspension, 10 week cross‐over treatment.
Participants	18 patients (4 women, 14 men) with essential hypertension, WHO stages 1 and 2, average age 55.9 years (range 42 to 66 years). Patients older than 70 years, renal failure or body weight > 90 kg excluded.
Interventions	Intervention: Monotherapy with 100 mg oral coenzyme Q10 daily for 10 weeks Control: Placebo
Outcomes	Resting supine SBP and DBP at 10 weeks
Notes	Sources of funding not stated. Small study size.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote "...patients were randomly assigned... then each patient in group A crossed over to placebo treatment and each patient in group B crossed over to CoQ treatment..." Does not describe the sequence generation process.
Allocation concealment (selection bias)	High risk	Insufficient information provided. Does not describe how allocation concealment was ensured.
Blinding (performance bias and detection bias) Blood Pressure	High risk	No information provided as to whether blinding was achieved.
Incomplete outcome data (attrition bias) Blood Pressure	Low risk	No missing outcome data.
Selective reporting (reporting bias)	High risk	BP reported was stated as end of treatment. BPs at other times were not reported.
Other bias	High risk	No indication as to how patients were selected, "eighteen subjects were selected from among those presenting with essential arterial hypertension," so they could have been selected based on previous response to CoQ10. BP standard deviations are lower and not as variable as would be expected.