Skip to main content

Table 4 Subgroup analyses comparing milk intake and hip fracture risk for case-control and cohort studies

From: Dairy product consumption and risk of hip fracture: a systematic review and meta-analysis

  Cohort studies (n = 9) Case-control studies (n = 7)
  n RR 95% CI I2 (%) P a P b n OR 95% CI I2 (%) P a P b
Study quality         
 Score ≥ 8 4 0.98 0.75–1.27 90.0 <0.01 0.90 4 0.80 0.67–0.95 10.0 0.34 0.05
 Score < 8 4 1.03 0.86–1.24 0.0 0.82   3 0.42 0.25–0.71 35.0 0.21  
Region             
 USA 4 1.00 0.96–1.03 0.0 0.84 0.44 1 1.10 0.63–1.94 NA NA 0.04
 Europe 3 0.98 0.68–1.41 86.0 <0.01   3 0.77 0.65–0.90 0.0 0.39  
 Asia 1 0.54 0.26–1.12     3 0.42 0.25–0.71 35.0 0.21  
Sex         
 Male 5 0.91 0.70–1.19 48.0 0.10 0.68 1 0.82 0.61–1.11 NA NA 0.28
 Female 6 1.07 0.78–1.47 81.0 <0.01   4 0.78 0.53–1.14 58.0 0.07  
 Both 3 0.91 0.70–1.18 23.8 0.23   2 0.46 0.25–0.85 44.0 0.18  
No. of cases         
 ≥ 1000 2 1.19 0.85–1.66 90.0 <0.01 0.16 1 0.71 0.58–0.87 NA NA 0.21
 100–1000 4 1.00 0.82–1.21 0.0 0.57   4 0.83 0.65–1.06 24.0 0.27  
 ≤ 100 6 0.79 0.60–1.04 46.0 0.10   2 0.28 0.15–0.55 0.0 0.84  
Duration of follow-up years         
 ≥ 10 years 5 1.02 0.84–1.25 86.0 <0.01 0.63 NA NA NA NA NA NA
 < 10 years 3 0.89 0.62–1.29 0.0 0.98   NA NA NA NA NA NA
Age         
 ≥ 70 4 1.00 0.96–1.03 0.0 0.80 0.45 3 0.61 0.34–1.09 68.0 0.04 0.66
 < 70 5 0.89 0.66–1.02 83.0 <0.01   4 0.76 0.57–1.01 52.0 0.10  
Adjustment for confounders             
 Smoking             
 Yes 5 1.06 0.87–1.29 85.0 <0.01 0.21 2 0.87 0.67–1.12 0.0 0.50 0.32
 No 3 0.78 0.55–1.11 0.0 0.52   5 0.60 0.42–0.88 60.0 0.04  
Alcohol             
 Yes 4 1.10 0.84–1.43 81.0 <0.01 0.18 2 0.87 0.67–1.12 0.0 0.50 0.32
 No 4 0.93 0.79–1.10 16.0 0.31   5 0.60 0.42–0.88 60.0 0.04  
BMI             
 Yes 5 1.00 0.77–1.29 79.0 <0.01 0.71 4 0.80 0.67–0.95 10.0 0.34 0.05
 No 3 0.99 0.96–1.03 0.0 0.83   3 0.42 0.25–0.71 35.0 0.21  
Physical activity             
 Yes 6 1.03 0.82–1.29 75.0 <0.01 0.47 2 0.72 0.52–1.00 37.0 0.21 0.93
 No 2 0.82 0.47–1.43 63.0 0.10   5 0.67 0.45–1.01 65.0 0.02  
Sunlight exposure             
 Yes 0 NA NA NA NA NA 2 0.74 0.63–0.88 0.0 0.43 0.67
 No 8 1.01 0.84–1.20 80.0 <0.01   5 0.62 0.38–1.01 67.0 0.02  
Total energy intake             
 Yes 5 1.11 0.91–1.35 86.0 <0.01 0.05 0 NA NA NA NA NA
 No 3 0.69 0.49–0.96 0.0 0.45   7 0.71 0.55–0.91 54.0 0.04  
Calcium and vitamin D supplementation             
 Yes 5 1.12 0.92–1.36 86.0 <0.01 0.04 0 NA NA NA NA NA
 No 3 0.69 0.50–0.95 0.0 0.47   7 0.71 0.55–0.91 54.0 0.04  
  1. Abbreviations: N, the number of studies; CI, confidence interval; OR, odds ratio; RR, relative risk; NA, not applicable; BMI, body mass index. Pa, heterogeneity within each subgroup; Pb, heterogeneity between subgroups with meta-regression analysis