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Table 4 Univariate random effects meta-regression (methods of moments) and subgroup analyses for GENDER (female)

From: Determinants of participation in voluntary work: a systematic review and meta-analysis of longitudinal cohort studies

  Subgroup analyses Results from meta-regression
Results Heterogeneity
Variable Subgroup Number of studies OR 95% CI P-value I 2 Coefficient SD P-value
Outcome measurement Mixed 2 1.224 0.895–1.674 0.800 0% Reference
Formal 9 (13 different samples) 1.061 0.907–1.243 0.000 89% −0.1424 0.2379 0.550
Proportion of volunteers (%) in baseline study sample Continuous 9a (13 different samples) 1.099 0.917–1.317 0.000 89% 0.0004 0.0003 0.177
0–100% 8 1.038 0.805–1.268 0.000 93% Reference   
0% 2 (3 different samples) 0.918 0.808–1.043 0.836 0% −0.0689 0.2266 0.761
100% 3 (4 different samples) 1.306 1.000–1.705 0.296 19% 0.2926 0.2156 0.175
Mean age at baseline Continuous 10b (13 different samples) 1.109 0.920–1.337 0.000 86% −0.0000 0.0006 0.952
≤ 55 years 6 (8 different samples) 1.136 0.939–1.374 0.000 85% Reference   
>  55 years 6 (7 different samples) 1.023 0.765–1.367 0.000 90% −0.1296 0.1695 0.445
Continent USA 6 1.279 1.120–1.460 0.063 52% Reference
Europe 5 (9 different samples) 0.906 0.770–1.067 0.000 77% −0.3531 0.1135 0.002
Year of baseline measurement Continuous 11c (15 different samples) 1.078 0.931–1.249 0.000 88% 0.0008 0.0126 0.951
<  2006 9 (11 different samples) 1.083 0.924–1.270 0.000 91% Reference   
≥ 2006 3 (4 different samples) 1.084 0.775–1.516 0.474 0% −0.0301 0.2334 0.897
Risk of bias items
 Study participation Unclear/high risk of bias 9 (11 different samples) 1.025 0.871–1.205 0.000 89% Reference
Low risk of bias 3 (4 different samples) 1.288 1.094–1.515 0.383 2% 0.2436 0.1809 0.178
 Study confounding Unclear/high risk of bias 1 1.174 0.748–1.842 N.A. N.A. Reference
Low risk of bias 10 (14 different samples) 1.073 0.922–1.250 0.000 89% −0.0898 0.3302 0.786
  1. aThe studies of Ajrouch et al. (2014) and Voorpostel & Coffé (2014) are not included in this analysis, because the proportion of volunteers (%) in the baseline study sample is not reported
  2. bThe study of Hank & Erlinghagen (2010) is not included in this analysis, because the mean age at baseline is not reported
  3. cThe study of Broese van Groenou & Van Tilburg (2012) includes two different samples in the analyses. For one of the samples, the year of baseline measurement is 1992, for the other sample, the year of baseline measurement is 2002. No separate results for the two samples are provided. In this specific analysis, we took 1992 as the year of baseline measurement, although this actually only is the case for the first sample
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