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Table 4 Patient characteristics associated with the presence of a potentially serious drug-drug interaction for people dispensed at least two drugs in 2010

From: The rising tide of polypharmacy and drug-drug interactions: population database analysis 1995–2010

Variable (no. of patients) Proportion (95% CI) with any DDI Univariate multilevel odds ratio (95% CI) Adjusted multilevel odds ratio (95% CI)
Age groups (years)    
20–29 (n = 9,976) 4.5 (4.0–5.0) Reference Reference
30–39 (n = 12,294) 9.2 (8.6–9.8) 2.18 (1.5–2.44) 1.88 (1.68–2.11)
40–49 (n = 18,805) 15.8 (14.9–16.6) 4.05 (3.65–4.49) 3.05 (2.75–3.39)
50–59 (n = 23,565) 25.1 (24.0–26.2) 7.28 (6.59–8.04) 4.67 (4.21–5.17)
60–69 (n = 30,756) 33.8 (32.8–34.8) 11.2 (10.1–12.3) 6.05 (5.47–6.69)
70–79 (n = 27,240) 42.5 (41.4–43.6) 16.2 (14.7–17.9) 6.98 (6.31–7.72)
80+ (n = 17,977) 46.0 (44.8–47.1) 18.8 (17.0–20.7) 7.34 (6.62–8.14)
Sex    
Male (n = 58,466) 30.7 (30.0–31.5) Reference Reference
Female (n = 82,147) 27.7 (27.0–28.4) 0.87 (0.85–0.88) 0.85 (0.83–0.88)
Place of residence    
Living in own home (n = 13,615) 28.7 (28.1–29.4) Reference Reference
Living in care home (n = 2,998) 38.0 (36.3–39.7) 1.51 (1.40–1.63) 0.51 (0.47–0.56)
No. of drugs dispensed in last 84 days    
2–4 (n = 71,427) 10.9 (10.4–11.4) Reference Reference
5–9 (n = 50,972) 40.0 (39.0–40.9) 5.49 (5.33–5.65) 4.39 (4.26–4.53)
10–14 (n = 14,662) 65.9 (64.9–67.0) 16.1 (15.5–16.8) 12.0 (11.5–12.5)
15+ (n = 3,552) 80.8 (79.4–82.2) 35.3 (32.3–38.5) 26.8 (24.5–29.3)
  1. Patient level socioeconomic deprivation and urban/rural residence, and practice level variables (list size, accreditation for postgraduate training, dispensing medicines, type of NHS contract) were not significant in either univariate or adjusted models and are not shown.