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Placebo and nocebo responses in essential tremor : a systematic review and meta-analysis
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Introdução O Tremor Essencial (TE) é a doença do movimento mais comum em adultos. Estudos anteriores reportam efeitos placebo clinicamente relevantes em doenças do movimento, como a doença de Parkinson e o síndrome das pernas inquietas. O nosso objetivo era quantificar a magnitude dos efeitos placebo e nocebo em doentes com TE.
Métodos Foi feita uma pesquisa em várias bases de dados e foram incluídos todos os estudos aleatorizados e controlados com doentes com TE, desde que reportassem pelo menos um outcome de interesse extraível no braço placebo. O efeito placebo foi definido como a diferença em relação à medição inicial na subescala C do Tremor Rating Scale(TRS) de Fahn-Tolosa-Marin. O efeito nocebo foi definido como a proporção de doentes que reportaram eventos adversos no braço placebo. As meta-análises foram realizadas usando métodos de efeitos aleatórios. A heterogeneidade estatística foi reportada usando a estatística I2. Foram ainda realizadas análises de subgrupos e de sensibilidade pré-definidas com o fim de explorar a heterogeneidade e as potenciais fontes de viés. O protocolo PROSPERO foi prospetivamente registado com o número CRD42018089306.
Resultados Foram incluídos 63 estudos (1231 participantes). O effect size para o efeito placebo foi –0.17 (95%CI: –0.31;–0.02), correspondendo a –2.07 pontos na subescala C do TRS. O efeito nocebo foi reportado em 29 estudos e obteve-se uma proporção de 13.59% (95%CI: 8.99;18.19) efeitos adversos no braço placebo. O efeito nocebo foi superior em estudos farmacológicos que usaram vias de administração não-oral e em estudos avaliados com risco de viés globalmente baixo. Não se verificou uma correlação estatisticamente significativa entre os efeitos placebo vs nocebo.
Conclusões A magnitude dos efeitos placebo e nocebo foi globalmente pequena, e não se obteve uma correlação estatisticamente significativa entre estes. Contudo, devido a questões metodológicas intrínsecas aos estudos incluídos, os resultados devem ser criticamente interpretados.
Background Essential Tremor (ET) is the most common movement disorder in adults. Previous studies report clinically important responses under placebo treatment in movement disorders such as Parkinson disease and restless legs syndrome. Our objective was to quantify the magnitude of the placebo and nocebo responses in patients with ET. Methods Databases were searched up to September 2017. Randomized placebo controlled trials of patients with ET were included if quantitative data were extractable in the placebo arm. Placebo response was defined as the within-group change from baseline in TRS subscore C. Nocebo response was defined as the proportion of patients experiencing adverse events in the placebo arm. Random-effects meta-analysis was used to pool data. Statistical heterogeneity was assessed with I2 statistic. Several predetermined subgroup and sensitivity analysis were performed to explore heterogeneity and potential sources of bias. The study is registered with PROSPERO, number CRD42018089306. Results Sixty-three randomized controlled trials, enrolling a total of 1,231 participants, were included. Pooled placebo response was –2.07 points in the TRS subscore C. The pooled nocebo response was 13.59% (95% CI 8.99 to 18.19, 29 trials, I2=66.9%). The nocebo response was greater in pharmacological studies using non-oral medications and in studies rated as having an overall low risk of bias. No statistically significant correlation was observed between placebo and nocebo responses. Conclusions The magnitudes of the placebo and nocebo responses in ET are small, with considerable different patterns of variation and no correlation between them. However, due to studies’ methodological issues, findings must be carefully interpreted.
Background Essential Tremor (ET) is the most common movement disorder in adults. Previous studies report clinically important responses under placebo treatment in movement disorders such as Parkinson disease and restless legs syndrome. Our objective was to quantify the magnitude of the placebo and nocebo responses in patients with ET. Methods Databases were searched up to September 2017. Randomized placebo controlled trials of patients with ET were included if quantitative data were extractable in the placebo arm. Placebo response was defined as the within-group change from baseline in TRS subscore C. Nocebo response was defined as the proportion of patients experiencing adverse events in the placebo arm. Random-effects meta-analysis was used to pool data. Statistical heterogeneity was assessed with I2 statistic. Several predetermined subgroup and sensitivity analysis were performed to explore heterogeneity and potential sources of bias. The study is registered with PROSPERO, number CRD42018089306. Results Sixty-three randomized controlled trials, enrolling a total of 1,231 participants, were included. Pooled placebo response was –2.07 points in the TRS subscore C. The pooled nocebo response was 13.59% (95% CI 8.99 to 18.19, 29 trials, I2=66.9%). The nocebo response was greater in pharmacological studies using non-oral medications and in studies rated as having an overall low risk of bias. No statistically significant correlation was observed between placebo and nocebo responses. Conclusions The magnitudes of the placebo and nocebo responses in ET are small, with considerable different patterns of variation and no correlation between them. However, due to studies’ methodological issues, findings must be carefully interpreted.
Descrição
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2019
Palavras-chave
Tremor essencial Placebo Nocebo Revisão sistemática