Background: Recruitment plays a vital role in conducting randomized control trials (RCTs). Challenges and failure of proper recruitment lead to early termination of trials. Monetary incentives have been suggested as a potential solution to these challenges. Therefore, we aimed to do a systematic review and analysis to evaluate the effect of incentives on the number of participants willing to consent to and participate in RCTs. Methods: Electronic databases were systematically searched from inception to September 23^rd, 2021, using the following keywords: payments, incentive, response, participation, enrollment, randomized, randomization, and RCT. The Cochrane Risk of Bias tool was used to assess the quality of the included trials. Risk ratios (RRs) were calculated with their corresponding 95% confidence interval (CI). All analyses were done with the random-effects model. We used Revman software to perform the analysis. Results: Six RCTs with 6,253 Participants met the inclusion criteria. Our analysis showed significant improvement in response rate (RR: 1.27; 95% CI: 1.04, 1.55; P = 0.02) and consent rates (RR: 1.44; 95% CI: 1.11, 1.85; P = 0.006) when an incentive payment was offered to participants. Even a small amount of incentive showed significant improvement in both consent (RR: 1.33; 95% CI: 1.03, 1.73; P = 0.03) and response rates (RR: 1.26; 95% CI: 1.08, 1.47; P = 0.004). Conclusion: In conclusion, our meta-analysis demonstrated statistically significant increases in the rate of consent and responses from participants when offered even small monetary value incentives. These findings suggest that incentives may be used to reduce the rate of recruitment failure and subsequent study termination. However, further RCTs are needed to establish a critical threshold beyond which incentive amount does not alter response rates further and the types of RCTs in which financial incentives are likely to be effective.

Background: Surveys are an effective method for collecting a large quantity of data. However, incomplete responses to these surveys can affect the validity of the studies and introduce bias. Recent studies have suggested that monetary incentives may increase survey response rates. We intended to perform a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of monetary incentives on survey participation.Methods: A systematic search of electronic databases was conducted to collect studies assessing the impact of monetary incentives on survey participation. The primary outcome of interest was the response rates to incentives: money, lottery, and voucher. We used the Cochrane Collaboration tool to assess the risk of bias in randomized trials. We calculated the rate ratio (RR) with its 95% confidence interval (95% CI) using Review Manager Software (version 5.3). We used random-effects analysis and considered the data statistically significant with a P-value <0.05.Results: Forty-six RCTs were included. A total of 109,648 participants from 14 countries were involved. The mean age of participants ranged from 15 to more than 60 years, with 27.5% being males, 16.7% being females, and the other 55.8% not reported. Our analysis showed a significant increase in response rate in the incentive group compared to the control group, irrespective of the incentive methods. Money was the most efficient way to increase the response rate (RR: 1.25; 95% CI: 1.16,1.35; P = < 0.00001) compared to voucher (RR: 1.19; 95% CI: 1.08,1.31; P = < 0.0005) and lottery (RR: 1.12; 95% CI: 1.03,1.22; P = < 0.009).Conclusion: Monetary incentives encourage the response rate in surveys. Money was more effective than vouchers or lotteries. Therefore, researchers may include money as an incentive to improve the response rate while conducting surveys.