Evidence-Based Medicine & Statistics

Absolute Risk Reduction ARR

TRMutlak Risk Azalması
Also known as:Risk difference Ā· Absolute risk difference

The arithmetic difference between the event rate in the control group and the event rate in the treated group, expressing the absolute benefit of a treatment over a defined period.

Formula

ARR = CER āˆ’ EER NNT = 1 / ARR

In depth

ARR depends on both the treatment effect and the baseline (control) risk, so the same relative effect gives a larger ARR in high-risk patients. It is expressed as a proportion or percentage over a stated time frame, and its reciprocal is the number needed to treat.

Example: if 10% of control and 6% of treated patients have an event over 5 years (CER, control event rate; EER, experimental event rate), ARR = 4 percentage points, RRR = 40% and NNT = 25 over 5 years. When treatment increases an adverse outcome, the corresponding difference is the absolute risk increase (ARI).

Clinical pearl

Absolute risk reduction is the most informative measure for counseling patients and should always be quoted with its time frame (e.g., 4% over 5 years).

TRIn Turkish

Mutlak Risk Azalması

Belirli bir sĆ¼re iƧinde kontrol grubundaki olay oranı ile tedavi grubundaki olay oranı arasındaki aritmetik farktır ve tedavinin mutlak yararını gƶsterir.

ARR hem tedavi etkisine hem de başlangıƧ (kontrol) riskine bağlıdır; bu nedenle aynı gƶreceli etki yĆ¼ksek riskli hastalarda daha bĆ¼yĆ¼k bir ARR sağlar. Belirtilen bir zaman dilimi iƧin oran ya da yĆ¼zde olarak ifade edilir ve tersi tedavi edilmesi gereken hasta sayısını (NNT) verir.

Ɩrnek: 5 yılda kontrol grubundaki hastaların %10'unda, tedavi grubundakilerin %6'sında olay gelişirse (CER: kontrol grubu olay oranı; EER: deney grubu olay oranı) ARR = 4 yĆ¼zde puanı, RRR = %40 ve 5 yıllık NNT = 25 olur. Tedavi olumsuz bir sonlanımı artırıyorsa karşılık gelen fark mutlak risk artışıdır (ARI).

Mutlak risk azalması hastaya danışmanlıkta en bilgilendirici ƶlĆ§Ć¼ttĆ¼r ve her zaman zaman dilimiyle birlikte belirtilmelidir (ƶrneğin 5 yılda %4).

Diğer adları:Mutlak risk azaltımı Ā· Risk farkı
Updated 24.09.2026 0 views Educational reference ā€” verify against current sources before clinical use.

Read next

Relative Risk ReductionGƶreceli Risk Azalması

The proportional reduction in the risk of an outcome in a treated group compared with a control group, calculated as the absolute risk reduction divided by the control event rate.

 Number Needed to TreatTedavi Edilmesi Gereken Hasta Sayısı

The average number of patients who need to be treated with an intervention for a specified period to prevent one additional adverse outcome compared with the control treatment.

 Relative RiskGƶreceli Risk

The ratio of the risk (cumulative incidence) of an outcome in an exposed or treated group to the risk in an unexposed or control group over the same period.

 Number Needed to HarmZarar Gƶrmesi İƧin Tedavi Edilmesi Gereken Hasta Sayısı

The average number of patients who need to be treated with an intervention for a specified period for one additional patient to experience a particular harm compared with the control treatment.