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Table 1 GRADE Quality of Evidence Assessment

From: The complex relationship between estrogen and migraines: a scoping review

Study

Study Design

Risk of Bias

Imprecision

Inconsistency

Indirectness

Publication Bias

Comments

Quality

Cachrimanidou 1993 [7]

RCT

Low

Not serious

Not serious

Not serious

Not serious

N/A

High

Brandes 2006 [5], Misakian 2003 [8]

Cross sectional

Low

Not serious

Not serious

Not serious

Not serious

Both studies used data from Women's Health Study

High

Amir 2005 [9]

Cross sectional

Low

Serious

Serious

Not serious

Not serious

Potential confounding from participants being treated with IVF. Inconsistency with other studies due to conclusion that GnRH therapy increased risk of migraine. Potential imprecision due to to small sample size.

Moderate

Calhoun 2008 [4]

Prospective cohort

Some

Serious

Serious

Not serious

Not serious

Potential confounding from participants having a history of medically intractable menstrual migraine. Inconsistency with other studies and imprecision due to 36% of participants in treatment group having no statistically significant change in outcome and being excluded from treatment group in final analysis.

Moderate

de Lignieres 1986 [10]

Double blind placebo-controlled crossover

Some

Serious

Not serious

Not serious

Not serious

Older age of participants and small sample size

Moderate

Facchinetti 2002 [11], Martin 2003 [12]

RCT

Some

Serious

Not serious

Not serious

Not serious

Older age of participants and small sample size

Moderate

MacGregor 2006 [13]

Double blind placebo-controlled crossover

Some

Serious

Not serious

Not serious

Not serious

Nonspecific participant selection criteria. Imprescision due to wide confidence intervals and small sample size

Moderate

Calhoun 2004 [14]

Open-label clinical trial

Some

Serious

Not serious

Not serious

Not serious

Lack of control and blinding. Imprecision due to small sample size and lack of control to compare results

Low

Johannes 1995 [15]

Self-reported 4-month diary

High

Serious

Not serious

Not serious

Not serious

Imprecision due to small sample size and lack of control to compare results

Low

Lichten 1995 [16]

Crossover

Some

Very serious

Not serious

Serious

Not serious

Potential confounding from participants having a history of medically intractable menstrual migraine. Indirectness present due to results not discussing the difference in response to treatment between participants, which is what the study design was for. Additionally, only women women that initially responded to treatment were progressed in the study. Considerable imprecision from small sample size and lack of consistent statistical analysis.

Low

Mattsson 2003 [17]

Survey

High

Very serious

Not serious

Not serious

Not serious

Increased risk of bias and imprecision due to self-reporting study design

Low

Pringsheim 2004 [6]

Survey

High

Very serious

Not serious

Not serious

Not serious

Increased risk of bias and imprecision due to self-reporting study design and lack of control group.

Low

Stewart 2000 [18]

Self-reported 98 day diary

High

Very serious

Not serious

Not serious

Not serious

Increased risk of bias and imprecision due to self-reporting study design and lack of control group.

Low

Lichten 1996 [19]

Open-label clinical trial

High

Very serious

Not serious

Not serious

Not serious

Lack of control group and single time administration. Imprecision due to small sample size and lack of control to compare results

Very low

Marcus 1999 [20], Murray 1997 [21]

Prospective cohort

High

Very serious

Serious

Not serious

Not serious

Very small sample sizes and potential confounding variables of pregnancy and / or hormone replacement therapy. Inconsistency due to conclusion that GnRH therapy decreased headache index. Imprecision due to small sample size and lack of control to compare results

Very low

Lichten 1996 [19]

Open-label clinical trial

High

Very serious

Not serious

Serious

Not serious

Small sample size and potential confounding from HRT use. Indirectness due to conclusions focusing on specific estrogen serum levels that precipitate migraine while study data focused on effect of timing in relation to withdrawal of estrogen on precipitation of migraine. Imprecision due to small sample size and lack of consistent statistical analysis

Very low

Somerville 1972 [22]

Crossover (case series)

High

Very serious

Not serious

Not serious

Serious

Small sample size and lack of statistical analysis. Potential risk of publication bias due to positive study results and being one of the first studies published on the topic. However this study is considered a landmark study in the field of hormonal migraines.

Very low