Propensity Score Matching Procedure Research Articles

Periodontal disease and risk of mortality and kidney function decline in advanced chronic kidney disease: a nationwide population-based cohort study.

Periodontal disease is prevalent in patients with chronic kidney disease (CKD) and potentially associated with kidney function decline. However, it is uncertain whether periodontal disease affects the risk of mortality and morbidity in patients with advanced CKD. Taiwan's National Health Insurance Research Database was used to conduct a nationwide population-based cohort study. Propensity score matching procedures were performed to select people with stage 5 CKD and to compare the long-term risk of mortality, end-stage renal disease, and major adverse cardiovascular events (MACE) between people with and without periodontal disease. Multivariable Cox regression analyses were conducted to calculate the adjusted hazard ratio (aHR) with 95% confidence interval (CI) for the outcome of interest. A total of 8119 subjects with stage 5 CKD were initially included. After matching to demographic and clinical covariates, 1254 subjects with 7099 person-years of follow-up were selected for analyses. Periodontal disease was not associated with long-term risks of all-cause mortality (aHR: 0.77, 95% CI: 0.49-1.22), progression to end-stage renal disease (aHR: 0.91, 95% CI: 0.75-1.10), or MACE (aHR: 1.18, 95% CI: 0.91-1.53). These findings were generally consistent across subgroups of age, sex, comorbid diabetes, uses of systemic antibiotic, and different dental procedures. Periodontal disease is not a predictor for long-term mortality or morbidity in patients with advanced CKD. These results provide important evidence to elucidate the relationship between periodontitis and critical clinical outcomes of advanced CKD.

LONG-TERM EFFECT OF ANTIHYPERTENSIVE AGENTS ON THE NEURAL BAROREFLEX SENSITIVITY-A SUBSTUDY OF THE PARIS PROSPECTIVE STUDY III

Objective: The baroreflex is a crucial mechanism regulating moment-to-moment blood pressure (BP) to ensure appropriate flow and pressure to the brain and other organs. All antihypertensive treatments, because of their BP lowering effect, interact with the autonomic nervous system by stimulating the sympathetic response. In addition, specific drugs may further interact with the BRS because of their specific mode of action. Whether antihypertensive agents have remnant effect is still unknown. Design and method: In the Paris Prospective Study III, spontaneous baroreflex, carotid stiffness and pharmacological drugs intake were available in 7967 adults (mean age of 60 ± 6 years, 62% men). The neural component of the baroreflex sensitivity (nBRS) was obtained with a cross-spectral analysis of variations in carotid distention rate and R-R intervals. Individuals with a BP lowering medication (BP-treated) were paired to non-BP treated individuals (controls) with similar cardiovascular comorbidities using a propensity score matching procedure (n = 1182 pairs). Results: Sympathetic activity was higher in the BP-treated group compared to their matched-controls, as shown by the increased spectral power of distention rate in the low frequency band (log LF distrate: 4.106 ± 0.530 vs 4.055 ± 0.514, p = 0.018). Amongst pharmacological classes of BP lowering agents, only agents acting on the angiotensin system (ACEi-ARB) were associated with nBRS. Compared to their matched controls (n = 331 pairs), ACEi-ARB users had lower nBRS (2.79 ± 0.66 (ln) vs. 2.90 ± 0.62 (ln), p = 0.03). After adjustment for carotid stiffness (stdbeta = 0.25, p < 0.001) and systolic pressure (stdbeta = -0.20, p < 0.001), ACEi-ARB remained significantly associated with nBRS (stdbeta = -0.09, p = 0.025). Conclusions: In this community-based population study, antihypertensive treatments induced activation of the autonomic nervous system independently of cardiovascular comorbidities. Taken as a whole, BP treatments did not have any effect on the neural component of the baroreflex loop, with the exception of ACEi-ARB which were negatively associated with nBRS. This effect was independent of BP and stiffness, which may suggest an inhibition of sympathetic activity by ACEi-ARB.

Impact assessment of agricultural technologies on household food consumption and dietary diversity in eastern Ethiopia

Food insecurity remains a major challenge to rural households in Eastern Ethiopia. To improve food and nutrition security of vulnerable households in eastern Ethiopia, several agricultural technologies have been scaled-up by Haramaya University for more than six decades. However, the impact of these technologies on household nutritional outcomes was not systematically studied. This study examined the impact of selected agricultural technologies on household food and nutrition security. Cross-sectional data were generated from 248 randomly selected rural households. Of these, 52% were non-users of improved agricultural technologies disseminated by the university while the remaining 48% sample respondents were users. The data generated from the field were analyzed using Propensity Score Matching (PSM) procedure and descriptive statistics. Results from the econometric analysis result show that households that adopted agricultural technologies had, on average, 8.97 higher Food Consumption Score (FCS) and 1.22 higher Household Dietary Diversity Score (HDDS) compared to those not using improved technologies. This shows that households adopting agricultural technologies are more likely to have higher food security compared to non-users. This suggests that promotion of improved agricultural technologies in the study area can enhance household food and nutrition security. • Improved agricultural technologies play vital role in rural household economies. • Households adopting improved agricultural technologies have higher HDDS and FCS. • Adopter households are more likely to have higher food security status. • Promoting improved agricultural technologies should be a priority for stakeholders.

Adoption of improved agricultural technology and its impact on household income: a propensity score matching estimation in eastern Ethiopia

BackgroundAdoption of improved agricultural technologies remains to be a promising strategy to achieve food security and poverty reduction in many developing countries. However, there are limited rigorous impact evaluations on the contributions of such technologies on household welfare. This paper investigates the impact of improved agricultural technology use on farm household income in eastern Ethiopia.MethodsPrimary data for the study was obtained from a random sample of 248 rural households, 119 of which are improved technology users and the rest are non-users. The research employed the Propensity Score Matching (PSM) procedure to establish the causal relationship between adoption of improved crop and livestock technologies and changes in farm income.ResultsResults from the econometric analysis show that households using improved agricultural technologies had, on average, 23,031.28 Birr (Birr is the official currency of Ethiopia. The exchange rate according to the National Bank of Ethiopia (NBE) was 1 USD = 27.6017 Birr on 04 October 2018.) higher annual farm income compared to those households not using such technologies. Our findings highlight the importance of promoting multiple and complementary agricultural technologies among rural smallholders.ConclusionsWe suggest that rural technology generation, dissemination and adoption interventions be strengthened. Moreover, the linkage among research, extension, universities and farmers needs to be enhanced through facilitating a multistakeholders innovation platforms.

Differences in employment concerns between Hispanic and Caucasian persons with multiple sclerosis: A propensity score matching analysis

BACKGROUND: Little is known about the experiences and concerns of Hispanic Americans with multiple sclerosis (MS), especially how their experiences and concerns compare to those of Caucasian Americans with MS. OBJECTIVE: The purpose of this study was to examine differences in satisfaction with the overall employment situation between two matched samples of adults with MS, namely, Hispanics and Caucasians. METHODS: Participants in this study responded to a national survey of the employment and community living concerns of people with MS. A propensity score matching (PSM) procedure was used to match participants based on demographic and MS-related variables. RESULTS: A two-sample Hotelling T2 test revealed no statistically significant between-group differences on satisfaction regarding fair treatment in the workplace but between-group differences were observed on satisfaction regarding legal rights and personal-environmental resources related to work. CONCLUSIONS: Implications for future research and clinical practice in rehabilitation counseling in the COVID-19 era are discussed.

Work and Race Matters: Examining the Relationship Between Two Critical Factors of College Completion at Four-Year Institutions

Research on college completion for students who work during their undergraduate education often approaches the topic from a financial perspective focused on aid and income status. This study takes a different approach by exploring the intersectionality of student employment and race, in relation to six-year bachelor's degree attainment. Based on a nationally representative sample of students attending four-year institutions in the United States and using propensity score matching procedures, the results highlight positive as well as negative associations of employment on bachelor's degree attainment, where the associations vary by race and the intensity of employment.

Significance of Anatomic Resection for the Patients with Primary Solitary Hepatocellular Carcinoma Located on the Liver Surface

Introduction: It is unclear whether anatomic resection achieves better outcomes than non-anatomic resection in patients with hepatocellular carcinoma (HCC). This study aimed to compare the outcomes of anatomic resection and non-anatomic resection for hepatocellular carcinoma located on the liver surface via one-to-one propensity score-matching analysis. Methods: Data from all consecutive patients who underwent liver resection for primary solitary hepatocellular carcinoma at Nara Medical University Hospital, Japan, January 2007- December 2015 were retrieved. Superficial hepatocellular carcinomas were defined as hepatocellular carcinoma that extended to a depth of < 3 cm from the liver surface and measured < 5 cm in diameter. The prognoses of the patients with superficial hepatocellular carcinoma who underwent anatomic resection and non-anatomic resection were compared. Results: In this study 23 patients with superficial hepatocellular carcinoma underwent anatomic resection, while 70 patients underwent non-anatomic resection. The recurrence-free survival rate of the patients who underwent anatomic resection was better than that of the patients who underwent non-anatomic resection (P = .006), while no such difference was observed for non-superficial hepatocellular carcinoma. After the propensity score-matching procedure, the resected liver volume and operation time were the only background or clinical characteristics to exhibit significant differences between the anatomic resection (n = 20) and non-anatomic resection groups (n = 20). The recurrence-free survival rate of the patients who underwent anatomic resection was significantly better than that of the patients that underwent non-anatomic resections (P = .030), but overall survival did not differ significantly between the groups (P = .182). Conclusions: Anatomic resection improves recurrence-free survival compared with non-anatomic resection in patients with superficial hepatocellular carcinoma.

Development of public stigma toward people with mental health problems in Czechia 2013-2019.

We aimed to assess the changes in public stigma towards people with mental health problems in Czechia; and to investigate the association between these and the exposure to the ongoing mental health care reform and one of its implementation projects focused on reducing stigma. We analyzed data from three cross-sectional surveys representative of the Czech adult population. We used linear regression models to compare population attitudes and desire for future contact with people with mental health problems between the 2013/2014 baseline and the 2019 follow-up. In our 2019 sample, we employed linear regression models to assess the relationship between exposure to mental health care reform and nation-wide anti-stigma campaign, and population stigmatizing attitudes and intended behavior. We utilized a propensity score matching procedure to mitigate potential bias. The 2013, 2014, and 2019 datasets consisted of 1797, 1810, and 1077 participants, respectively. Population attitudes improved significantly between 2014 and 2019 (B = 0.99, 95% CI = 0.06; 1.93), but we did not detect a change in population desire for future contact with people with mental health problems. Exposure to the nationwide anti-stigma campaign or mental health care reform was associated with more favorable attitudes (B = 4.25, 95% CI = 2.07; 6.42 and B = 7.66, 95% CI = 3.91; 11.42), but not with higher desire for future contact with people with mental health problems. Mental health care reform and its nation-wide anti-stigma project seems to have a positive impact on population attitudes, but not on desire for future contact with people with mental health problems.

Natural disasters and electoral outcomes

Natural disasters are good examples of catastrophic events that may affect vote decisions. In this study, we analyze how the occurrence of earthquakes changes voters' behavior at municipal elections and which channels drive this change, focusing in particular on the role of media exposure. We exploit data from 13,338 municipal electoral cycles where incumbents seek reelection between 1993 and 2015 in Italy. We apply a difference-in-difference strategy with time and cities fixed effect to the probability of reelection and vote share using three different control groups: the universe of municipalities, a sub-sample of neighboring municipalities, and a sub-sample of municipalities identified by a one-to-one nearest-neighbor propensity score matching procedure. We find that the occurrence of destructive earthquakes significantly increases the incumbent mayors’ chance of being reelected and their vote share. We argue that this result is driven by the incumbent mayor advantage in offering recovery from disaster damages combined with a higher visibility on the media in the aftermath of the disaster. Thus, the mediatic relevance of earthquake occurrence may bias voters towards the incumbent.

The protective effect of statins against pressure ulcers in stroke patients: A propensity-score matched study based on a real-world database

Background and aimsLimited information is available regarding the association between statins and pressure ulcers. The purpose of this study is to evaluate the beneficial effects of statins on pressure ulcers in stroke patients. MethodsUsing the claims data of Taiwan's National Health Insurance, we conducted a retrospective cohort study and identified new-onset stroke patients in 2000–2004. The propensity-score matching procedure was used to select eligible stroke patients with (n = 49,919) and without (n = 49,919) the use of statins. These two groups were followed until the end of 2009 to track the occurrence of pressure ulcers. Multivariate Cox proportional hazard models were conducted to calculate adjusted hazard rations (HRs) and 95% confidence intervals (CIs) of pressure ulcer associated with the use of statins. ResultsStroke patients who used statins had a reduced risk of pressure ulcers during the follow-up period (HR 0.74, 95% CI 0.71–0.78). The association between statin use and a reduced risk of poststroke pressure ulcers was significant in men (HR 0.73, 95% CI 0.68–0.78), women (HR 0.75, 95% CI 0.71–0.80), and people aged more than 50 years. Use of lovastatin, pravastatin, rosuvastatin, atrovastatin, fluvastatin, and simvastatin was associated with reduced poststroke pressure ulcers. There was a dose-dependent decrease in the frequency of pressure ulcers with increasing quantities of statins used, from 1 prescription to ≥3 prescriptions. ConclusionWe raised the possibility that use of statins was associated with reduced risk of pressure ulcers in stroke patients. However, the potential beneficial effect associated with statins requires further validation using randomized clinical trials.

Adverse outcomes after major surgery in children with intellectual disability.

To evaluate outcomes after major surgery in children and adolescents with intellectual disability. We used 2004 to 2013 claims data from Taiwan's National Health Insurance programme to conduct a nested cohort study, which included 220292 surgical patients aged 6 to 17years. A propensity score matching procedure was used to select 2173 children with intellectual disability and 21730 children without intellectual disability for comparison. Logistic regression was used to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of the postoperative complications and 30-day mortality associated with intellectual disability. Children with intellectual disability had a higher risk of postoperative pneumonia (OR 2.16, 95% CI 1.48-3.15; p<0.001), sepsis (OR 1.67, 95% CI 1.28-2.18; p<0.001), and 30-day mortality (OR 2.04, 95% CI 1.05-3.93; p=0.013) compared with children without intellectual disability. Children with intellectual disability also had longer lengths of hospital stay (p<0.001) and higher medical expenditure (p<0.001) when compared with children with no intellectual disability. Children with intellectual disability experienced more complications and higher 30-day mortality after surgery when compared with children without intellectual disability. There is an urgent need to revise the protocols for the perioperative care of this specific population. Surgical patients with intellectual disability are at increased risk of postoperative pneumonia, sepsis, and 30-day mortality. Intellectual disability is associated with higher medical expenditure and increased length of stay in hospital after surgical procedures. The influence of intellectual disability on postoperative outcomes is consistent in both sexes and those aged 10 to 17 years. Low income and a history of fractures significantly impacts postoperative adverse events for patients with intellectual disability.

Effects of Agricultural Cooperative Society on Farmers’ Technical Efficiency: Evidence from Stochastic Frontier Analysis

The impact of agricultural cooperatives on apple farmers’ technical efficiency (TE) in China was examined. The cooperatives were divided into two groups: a collective marketing group for farmers and an equivalent non-marketing group that did not provide a marketing service, although other functions remained the same. Using the propensity score matching (PSM) procedure and stochastic production frontier (SPF) modelling, cooperatives’ key functions that potentially increase farmers’ TE can be identified. The results indicate that membership of either group is positively related to yield. However, cooperatives that were not engaged in marketing achieved higher TE than non-members. This suggests that policy makers should encourage cooperatives to focus on activities that do not include direct marketing to increase TE in apple production in China.

Does participating in the standards-setting process promote innovation? Evidence from China

This paper provides novel empirical evidence on the positive effect of standards-setting involvements on corporate innovation in China, reflecting in improving the patent quantity and patent quality. This kind of positive effect increases as the firm's top management team quality increases. We also show that the positive effect of standards-setting involvements is more evident for state-owned enterprises than non-state-owned enterprises due to the unique features of state-owned enterprises. Our results are robust to a battery of tests, including the use of alternative model specifications, firm fixed effects, the instrumental variable approach, potential omitted variables, and propensity score matching procedure. Further analysis reveals that standards-setting involvements foster innovation mainly through improving firms' R&D efficiency, reducing financial constraints, and inducing collaborative innovation. Overall, our findings suggest that standards-setting involvements matter for corporate innovation in China.

Improving boys' reading comprehension with readers theatre

Research on readers theatre has indicated that it can improve elementary students' reading achievement and can be motivating, engaging and enjoyable, even for reluctant or struggling readers. Because of the potential for improvement and the engagement factor, the purpose of this study was to examine the effects of readers theatre on young male students, a population that tends to be more reluctant to read. This matched quasi‐experimental study examined the differential effects of readers theatre on second‐grade boys' decoding, word knowledge and reading comprehension. Students were pretested and posttested using the Gates‐MacGinitie Reading Test. With the use ofa propensity score matching procedure, 46 students were matched from a sample of 76 on the basis of pretest scores, English‐language learner status, at‐risk status and whether the students received special education services. A repeated measures analysis of variance detected a time effect on the reading comprehension measure, which was qualified by an interaction effect, indicating that boys in the treatment group outperformed those in the business‐as‐usual comparison group. Implementing readers theatre in elementary classrooms may be an effective means for engaging young male students in the reading process and improving their reading comprehension. Additional implications for instruction, limitations and directions for future research are also discussed.

Postoperative outcomes after total hip arthroplasty in patients with Parkinson disease: A protocol of case control study.

Background:Parkinson disease (PD) is a progressive neuromuscular disease associated with bradykinesia, tremor, and postural instability. We aimed to compare outcomes and complications of total hip arthroplasty (THA) between patients with PD and those without.Methods:A single institution retrospective cohort from 2000 to 2018 was reviewed. PD patients were matched 1:2 with non-PD control patients for age, gender, American Society of Anesthesiologists score, and body mass index using a propensity score matching procedure. The primary outcome measures were postoperative complications and revision between PD and cohort groups. Secondary outcome measures were Harris Hip Score, hip range of motion, patient satisfaction, and surgery time. Univariable and multivariable logistic regression were used to determine the relationship between PD and surgical outcomes in the matched cohort.Results:Using prospectively collated data, we identified 35 PD patients after primary THA. A control cohort of 70 primary THA patients was matched.Conclusion:Our hypothesis was that PD would have adverse impact on complication rates, range of movement, or improvement in functional outcome after subsequent THA.Trial registration:This study protocol was registered in Research Registry (researchregistry5446).

Sex differences in fracture outcomes within Taiwan population: A nationwide matched study.

Background and aimsBecause the sex difference in outcomes of fracture was incompletely understood, we evaluated the post-fracture complications and mortality of female and male patients.MethodsWe conducted a nationwide study of 498,586 fracture patients who received inpatient care using Taiwan’s National Health Insurance Research Database 2008–2013 claims data. Female and male fracture patients were selected for comparison by using a propensity-score matching procedure. Age, low income, types of fracture, fracture with surgery, several medical conditions, number of hospitalization and emergency visits were considered as potential confounding factors. Multivariate logistic regressions were used to calculate the adjusted odds ratios (OR), the 95% CI of post-fracture complications and 30-day in-hospital mortality differences between women and men.ResultsMale patients had a higher risk of post-fracture pneumonia (OR 1.96, 95% CI 1.83–2.11), acute renal failure (OR 1.85, 95% CI 1.60–2.15), deep wound infection (OR 1.63, 95% CI 1.51–1.77), stroke (OR 1.58, 95% CI 1.49–1.67), septicemia (OR 1.51, 95% CI 1.42–1.61), acute myocardial infarction (OR 1.38, 95% CI 1.09–1.75) and 30-day in-hospital mortality (OR 1.69, 95% CI 1.48–1.93) compared with female patients. However, a lower risk of post-fracture urinary tract infection (OR 0.69, 95% CI 0.65–0.72) was found in men than in women. Male patients also had longer hospital stays and higher medical expenditures due to fracture admission than did the female patients. Higher rates of post-fracture adverse events in male patients were noted in all age groups and all types of fractures.ConclusionWe raised the possibility that male patients showed more complications and higher mortality rates after fracture admission compared with female patients, with the exception of urinary tract infections.

Alcohol consumption and employment: a cross-sectional study of office workers and unemployed people.

BackgroundAlcohol is a psychoactive substance with toxic and addictive properties. Biomarkers like GGT, AST, ALT and MCV are influenced by excessive ethanol consumption. Alcohol consumption represents a health risk and it has been linked to unemployment. The aim of this study how working status predict alcohol consumption through a cross sectional study comparing alcohol-related biomarkers levels in office workers and unemployed people.MethodsThis study includes 157 office workers and 157 unemployed people, who were recruited from January to December 2018. A propensity score matching procedure was applied to obtain two homogenous groups in terms of age and gender. A non-parametric analysis was performed on serum biomarkers that are generally altered by alcohol consumption. Logistic regression models were designed to evaluate how working status predict abnormal biomarker levels related with alcohol consumption.ResultsNo differences in median biomarker values were found between groups. Logistic regression analysis showed that office work is a negative predictor of pathological biomarker levels. Office workers had a significant relation with the levels of GGT (OR 0.48; 95% CI [0.28–0.84]), AST (OR 0.42; 95% CI [0.22–0.78]), ALT (OR 0.39; 95% CI [0.23–0.66]), and MCV (OR 0.37; 95% CI [0.19–0.70]).ConclusionOffice workers had lower absolute frequencies of pathological values of alcohol consumption biomarkers, after matching for age and gender compared with unemployed people. In addition, a significant negative association between office work is a negative predictor of biomarker levels of alcohol consumption. These results showed that work is an important determinant of health and that can represent a benefit for workers in terms of reducing the risk of consuming alcohol.

Inconvenient Samples: Modeling Biases Related to Parental Consent by Coupling Observational and Experimental Results.

In studies involving human subjects, voluntary participation may lead to sampling bias, thus limiting the generalizability of findings. This effect may be especially pronounced in developmental studies, where parents serve as both the primary environmental input and decision maker of whether their child participates in a study. We present a novel empirical and modeling approach to estimate how parental consent may bias measurements of children’s behavior. Specifically, we coupled naturalistic observations of parent–child interactions in public spaces with a behavioral test with children, and used modeling methods to impute the behavior of children who did not participate. Results showed that parents’ tendency to use questions to teach was associated with both children’s behavior in the test and parents’ tendency to participate. Exploiting these associations with a model-based multiple imputation and a propensity score–matching procedure, we estimated that the means of the participating and not-participating groups could differ as much as 0.23 standard deviations for the test measurements, and standard deviations themselves are likely underestimated. These results suggest that ignoring factors associated with consent may lead to systematic biases when generalizing beyond lab samples, and the proposed general approach provides a way to estimate these biases in future research.

Comparable Efficacy and Safety of Generic Imatinib and Branded Imatinib in Patients With Newly Diagnosed Chronic Myeloid Leukemia With a Consideration of Socioeconomic Characteristics: A Retrospective Study From a Single Center

IntroductionTo compare the efficacy and safety of generic and branded imatinib in adults with newly diagnosed chronic myeloid leukemia in the chronic phase (CML-CP), we retrospectively reviewed data from patients CML-CP who received generic or branded imatinib. Patients and MethodsA propensity score matching (PSM) study was performed. A Cox regression model was used to identify factors associated with responses and outcomes. ResultsFour hundred forty-two adults receiving generic imatinib (n = 236) or Glivec (Novartis, Basel, Switzerland; n = 206) were included. There were more patients with rural household registration (P < .001), lower education level (P < .001), divorced or widowed status (P = .009), higher white blood cell counts (P = .019), splenomegaly (P < .001), and longer intervals from diagnosis to imatinib initiation (P = .033) in the generic cohort. During the follow-up, there was no significant difference between the 2 cohorts in the 4-year probabilities of achieving a complete cytogenetic response (97.0% vs. 97.3%; P = .736), major molecular response (87.8% vs. 90.1%; P = .113), and molecular response4.5 (32.5% vs. 38.8%; P = .186), as well as failure-free survival (77.3% vs. 81.4%; P = .313), progression-free survival (94.4% vs. 95.8%; P = .489), and overall survival (96.8% vs. 98.3%; P = .088). Multivariate analyses showed that the drug type was not associated with responses and outcomes. After the PSM procedure, 177 pairs of patients with comparable baseline characteristics were reanalyzed. Multivariate analyses confirmed that generic or branded imatinib used as first-line therapy was not associated with either responses or outcomes. ConclusionSociodemographic characteristics might influence the tyrosine kinase inhibitor that patients chose. Generic and branded imatinib as first-line therapy had comparable efficacy and safety in CML-CP patients.

Does firm size affect learning-by-exporting? Empirical evidence from Sub-Saharan Africa

This study examines whether the relationship between exports and productivity growth differs across firm size. Using panel data from three Sub-Saharan African countries, I use propensity score matching procedure to examine this relationship. This study finds evidence of productivity differences between new exporters and non-exporters confirming the empirical regularity that new exporters are more productive than never exporters. The findings indicate that export participation effects vary across firm size, with both small and large firms experiencing immediate and significant productivity gains upon entry. However, the productivity gain for large firms is highly significant and more pronounced in the first two years after entry but declines drastically from the third year and tends towards negative in subsequent years. Learning effects might be important for large firms during the initial years of exporting, but these effects dissipate once learning avenues have been exhausted. Small firms display sustained learning effects that expand beyond the fourth year. Relative to the large firms, small new exporters display sustained and significant productivity growth for five year. This study finds no evidence of cumulative productivity growth beyond the third year for large firms. These results are robust to alternative measure of productivity. Any export-led growth should be directed at helping small new exporters access the export markets.