Tipos de estudios

Se incluyeron ensayos controlados aleatorios (ECA) y el primer período de ECA cruzados. Se excluyeron los ensayos controlados cuasialeatorios (ensayos en que la asignación al tratamiento se hizo mediante un método no aleatorio como la alternancia) porque el método de asignación puede llevar a sesgo en los cálculos del efecto. No se restringió la elegibilidad de los estudios por el idioma ni el estado de publicación.

Sólo se incluyeron estudios de economía sanitaria realizados junto con los estudios incluidos en el componente clínico de esta revisión sistemática (Shemilt 2011).

Tipos de participantes

Se incluyeron estudios que incorporaron a mujeres a partir de los 18 años con diagnóstico de incontinencia urinaria sobre la base de los signos, los síntomas o la evaluación urodinámica (según la definición de los autores de los ensayos). Sólo se incluyeron ensayos que incorporaron a hombres y mujeres si al menos un 90% de los participantes eran mujeres o si el ensayo presentaba datos de resultados y demográficos de las mujeres por separado. Se incluyeron ensayos que incorporaron mujeres con diagnóstico de incontinencia urinaria de esfuerzo, urgencia o mixta, así como ensayos con participantes que presentaban tipos mixtos o no clasificados de incontinencia urinaria.

Se incluyeron ensayos realizados en mujeres que presentaban incontinencia urinaria durante el período pre o posnatal. Dado que este grupo presenta diferencias fisiológicas con respecto a las mujeres no embarazadas o después del parto, y la evolución natural de la incontinencia en esta población es diferente de las pacientes no embarazadas, pueden diferir en este grupo los efectos de la intervención observados. Por lo tanto, no se agrupó a esta población con las pacientes que no estaban embarazadas o en posparto y se programó analizar los estudios por separado en toda la revisión.

Se excluyeron los estudios de pacientes en quienes la incontinencia urinaria se asoció a factores no relacionados con las vías urinarias, como los trastornos neurológicos o psiquiátricos, la deficiencia cognitiva o los trastornos de movilidad. También se excluyeron los estudios centrados en mujeres con enuresis nocturna.

Tipos de intervenciones

Se incluyeron estudios de yoga como tratamiento para la incontinencia urinaria, cuando el informe del estudio especificaba que la intervención era de "yoga" proporcionado en cualquier dosis, con cualquier frecuencia y de cualquier duración, porque se piensa que es probable que estos factores tengan variabilidad en la práctica.

Se incluyeron intervenciones que pertenecían a cualquier tradición de yoga pero se excluyeron los estudios en que la intervención de yoga no comprendía un componente de práctica física. Se incluyeron estudios que compararon el yoga con ningún tratamiento o con otro tratamiento activo. También se incluyeron estudios que compararon el yoga como complemento de otros tratamientos versus los mismos tratamientos sin el yoga. Los tipos de comparaciones incluidas fueron los siguientes.

• Yoga versus ninguna intervención activa específica (p.ej. atención habitual, lista de espera).

• Yoga versus una intervención activa (p.ej. intervención del estilo de vida o entrenamiento muscular del suelo pelviano), para la que se consideraron diferentes comparadores activos por separado (p.ej. yoga versus asesoramiento del estilo de vida, yoga versus entrenamiento muscular del suelo pelviano).

• Yoga más una intervención versus la misma intervención sin yoga (p.ej. yoga como intervención adicional al entrenamiento del suelo pelviano versus entrenamiento del suelo pelviano solo), para lo cual se consideraron diferentes intervenciones por separado.

Se incluyeron estudios en que se proporcionaron cointervenciones si eran similares entre los grupos de intervención (p.ej. los grupos de yoga y de comparación recibieron asesoramiento sobre técnicas de terapia conductual).

No parecen ser habituales los estudios que comparan el yoga con una intervención de yoga simulada (Park 2014). Sin embargo, se programó considerar que estudios representen un tipo adicional de comparación (es decir, yoga versus yoga simulada) y se los analizaría por separado.

Se excluyeron los estudios de intervenciones basadas en el yoga (p.ej. ejercicios basados en las posturas de yoga) pero no caracterizadas como yoga, así como los estudios de intervenciones multimodales en que el yoga es sólo un componente entre otros, como la reducción del estrés basada en la atención plena (REBAP).

Tipos de medida de resultado

Se utilizaron los resultados sugeridos por el Standardisation Committee of the International Continence Society (Bø 2017; Haylen 2010). Las cinco categorías de resultados siguientes se recomiendan para la investigación del efecto de las intervenciones terapéuticas en mujeres con incontinencia urinaria (Lose 2001):

• observaciones de la paciente (p.ej. síntomas);

• cuantificación de los síntomas de la paciente (p.ej. pérdida de orina);

• observaciones del médico (signos anatómicos y funcionales);

• calidad de vida de la paciente (incontinencia urinaria: específica y general);

• medidas económicas.

En esta revisión, se consideró al menos un resultado de cada una de las cuatro primeras categorías. Se incluyeron resultados específicos hallados comúnmente en otras revisiones Cochrane sobre incontinencia urinaria en mujeres, de modo que con esta revisión se puedan obtener resultados que se puedan comparar o combinar fácilmente con los de otras revisiones sobre el tratamiento para la misma enfermedad.

Búsquedas electrónicas

Búsqueda de otros recursos

We checked the reference lists of all included studies and systematic reviews for additional references. We contacted experts in the field and authors of included studies to identify additional unpublished studies. We also checked the proceedings of the following conferences for relevant research:

• International Congress on Complementary Medicine Research (ICCMR) (2010 to 2017); and

• European Congress for Integrative Medicine (ECIM) (2009, 2011 to 2017).

Selección de los estudios

Two review authors independently screened the titles and abstracts of all retrieved references in Covidence (Covidence 2017). We retrieved the full‐text study reports for all citations that at least one review author considered potentially relevant. Two review authors independently screened the full‐text articles and identified studies for inclusion and identified and recorded reasons for excluded studies in the Characteristics of excluded studies. Any disagreements were resolved by discussion.

We collated multiple reports of the same study so that each study, rather than each report, was the unit of interest in the review. We recorded the selection process in sufficient detail to complete a PRISMA flow diagram (Moher 2009).

Extracción y manejo de los datos

We used a standardised piloted data collection form in Microsoft Excel 2018 for Mac Version 16.20 and extracted the following study characteristics and outcome data.

• Methods: study design.

• Participants: number randomised, number with each type(s) of incontinence and how incontinence was diagnosed, if participants were pregnant or postpartum, how many were pregnant and how many were postpartum, severity and duration of urinary incontinence if reported, study participant mean age or age range, study location and setting, recruitment methods and inclusion and exclusion criteria.

• Interventions: description of yoga intervention characteristics, dose and duration of yoga intervention, description of comparison intervention characteristics, adherence to the yoga and comparison interventions, description of any co‐interventions, length of follow‐up, number of withdrawals and reasons for withdrawal.

• Outcomes: description of primary and secondary outcomes in the review that were reported in the trial, and listing of other outcomes collected in the trial.

• Notes: funding for trial and notable conflicts of interest of trial authors.

• 'Risk of bias' assessment.

Two review authors independently extracted outcome data from the included studies into Microsoft Excel 2018 spreadsheets and compared the data to identify any discrepancies in data entry. Any disagreements were resolved by consensus. We noted in the Characteristics of included studies if a trial did not report outcome data in a usable way. We transferred all outcome data into Cochrane’s Review Manager 5 software (Review Manager 2014).

In addition to extracting data from included studies as described above, we planned to include an appendix of bibliographic detail of any identified economic studies. As such, we did not conduct a further review of potential economic studies.

Evaluación del riesgo de sesgo de los estudios incluidos

Two review authors (LSW, ZSL) independently assessed the risk of bias for each included trial using Cochrane's 'Risk of bias' tool (Higgins 2011a). Any disagreements were resolved by discussion. We assessed the risk of bias for the following domains: random sequence generation (selection bias), allocation concealment (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessment for each outcome (detection bias), incomplete outcome data (attrition bias), selective outcome reporting (reporting bias) and other bias (such as validity of outcome measure and baseline comparability).

We assessed each potential source of bias as either high, low, or unclear and provided a quotation from the study report together with a justification for our judgement in the 'Risk of bias’ tables. We summarised the judgements across different studies for each of the domains listed.

The participants and personnel in most yoga trials are not blinded. As the primary outcomes of this review depended upon the perception and reporting of the study participant, we have not included blinding of personnel, participants or outcome assessors in our dichotomising of trials into higher versus lower risk of bias. Instead, for our sensitivity analyses of the primary outcomes by higher versus lower risk of bias, we classified studies as having a relatively lower risk of bias if they had a low risk of bias for random allocation, allocation concealment and incomplete outcome assessment, and did not have a high risk of bias for selective outcome reporting or other bias (see Sensitivity analysis).

Medidas del efecto del tratamiento

We uploaded the outcome data for each study into the data tables in Review Manager 5 to calculate treatment effects (Review Manager 2014). We used the risk ratio (RR) for dichotomous outcomes related to benefit of treatment (e.g. cure). We used the absolute risk difference (RD) for adverse events. We used the mean difference (MD) for continuous outcomes reported on the same scale, and the standardised mean difference (SMD) for continuous outcomes measured on different scales in different trials included in the same meta‐analysis. We expressed the uncertainty with 95% confidence intervals (CIs) for all effect estimates.

If the included studies only reported effect estimates and their CIs, standard errors or exact P values, we uploaded these data into Review Manager 5 in order to apply the generic inverse variance method (Review Manager 2014). We ensured that higher scores for continuous outcomes had the same meaning for a given outcome and explained the direction to the reader. When we were unable to enter the results in either of the above ways, we described them in the Characteristics of included studies or entered the data into the Additional tables.

Cuestiones relativas a la unidad de análisis

Where appropriate, we planned to include the first period of cross‐over studies. We also planned to include cluster‐randomised studies if they were suitable according to the guidance in Chapter 16 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011b).

Manejo de los datos faltantes

We contacted investigators or study sponsors in order to verify key study characteristics and to obtain missing numerical outcome data where possible. If numerical outcome data such as standard deviations (SDs) or correlation coefficients were missing, we attempted to calculate them from other available statistics, such as P values, according to the methods described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011a). If we were unable to obtain a full report even after contacting the study authors, we listed the study as 'awaiting classification'.

Evaluación de la heterogeneidad

We assessed clinical heterogeneity (i.e. differences in study populations, interventions and outcomes) between studies qualitatively. For studies that we judged to have sufficient clinical homogeneity to combine in a meta‐analysis, we planned to assess heterogeneity in three ways: visual examination of the forest plots; the Chi² test (P ≤ 0.10) for heterogeneity; and the I² statistic, which describes the per cent of the variability in the estimate that is due to clinical or methodological heterogeneity rather than to chance. We planned to consider the implications of the observed value of the I² statistic as follows:

• 0% to 40%: might not be important;

• 30% to 60%: may represent moderate heterogeneity;

• 50% to 90%: may represent substantial heterogeneity;

• 75% to 100%: considerable heterogeneity (Deeks 2011).

We planned to assess the importance of the value of the I² statistic in light of the range and direction of effects as observed from the forest plots and the strength of the evidence for heterogeneity based upon the Chi² test (Deeks 2011). We planned to seek and discuss plausible explanations for observed statistical heterogeneity. We planned to investigate causes of heterogeneity between trials, qualitatively assessing any differences between individual trials in the populations and interventions. We also planned to explore heterogeneity through the use of subgroup and sensitivity analyses.

Evaluación de los sesgos de notificación

We searched study registries of prospectively registered trials to identify completed, but not published, trials. We planned to use a funnel plot and Egger's test to assess the potential for publication bias in meta‐analyses with more than 10 trials (Egger 1997; Sterne 2011).

Síntesis de los datos

Where trials were clinically comparable (i.e. clinical comparability of population, intervention, comparison, outcome and timing of measurement), we planned to combine the outcome data from the individual trials in a meta‐analysis using Review Manager 5 (Review Manager 2014). We planned to analyse pregnant and postpartum women separately in call cases. However, for non‐pregnant, non‐postpartum populations, we planned to group together women with SUI, UUI, MUI and mixed or unclear urinary incontinence diagnoses in the primary analysis, and examine different types of urinary incontinence diagnoses using subgroup analyses (see Subgroup analysis and investigation of heterogeneity).

As yoga is a complex intervention with variations in practice components and implementation and we expected some between‐study variation due to these factors, we planned to use the random‐effects model for meta‐analysis.

When outcome data from individual trials were not sufficiently similar to be combined quantitatively, we planned to narratively describe the results from clinically comparable trials.

Análisis de subgrupos e investigación de la heterogeneidad

As the mechanisms of SUI and UUI are different, the effects of yoga may vary across types of urinary incontinence. We planned that if there were sufficient data, we would carry out subgroup analyses by type of urinary incontinence in the following groups:

• SUI;

• UUI;

• MUI; and

• a range of urinary incontinence diagnoses, where data are not reported separately by urinary incontinence subgroup.

If sufficient data become available, we also plan to conduct subgroup analyses of trials conducted in older (mean age 65 years or greater) versus younger populations, as populations from different age groups may vary in their ability to perform yoga. Among women who are pregnant or postpartum, we plan to perform subgroup analyses of trials conducted in women who are pregnant versus postpartum, as the natural history of incontinence is different in the two states. We also intend to carry out subgroup analyses by style (e.g. Iyengar yoga, Viniyoga, Yin yoga), dose and duration of yoga intervention to determine whether type of yoga, amount of yoga or duration of yoga modifies the effect of the yoga intervention.

Análisis de sensibilidad

When both endpoint and change data were available, we used endpoint data for our primary analysis and carried out a sensitivity analysis to check whether the results varied according to endpoint versus change data. In cases where study participants were lost to follow‐up and intention‐to‐treat analyses were conducted using imputation alongside available‐case analyses, we used the observed data for our primary analysis and performed a sensitivity analysis to check whether the results varied according to imputed versus available‐case data. In cases where both unadjusted and adjusted data were available, we used the unadjusted data for our primary analysis and performed a sensitivity analysis to check whether the results varied according to adjusted versus unadjusted data.

If sufficient data become available, we plan to assess the robustness of our conclusions by excluding studies that we judge to have a high risk of bias from our meta‐analyses for the primary outcomes.