Is age associated with different vital signs in adults presenting to hospital with bacterial infection? A systematic review and meta-analysis

Abstract

Background: It has long been suspected that the vital sign abnormalities that accompany bacterial infection are subtle or absent in older adults. This review summarises the evidence for whether older adults present with different vital sign abnormalities to younger adults when hospitalised with bacterial infection.

Methods: MEDLINE, EMBASE and CINAHL EBSCO were searched from inception to 19 December 2024 for English-language research articles of patients hospitalised with bacterial infection reporting age and admission vital signs. We used meta-regression to assess how vital signs vary with age. Where studies reported vital signs in multiple age groups, we undertook a meta-analysis in younger (<65) and older patients (≥65). Evidence quality was assessed using an adapted Quality Assessment of Diagnostic Accuracy Studies-2 tool.

Results: Our search yielded 14 487 studies; 132 were included after screening. Older adults were less likely to be tachycardic (RR 0.82, 0.69 to 0.97, I2 = 86.5%) with a mean difference in heart rate of 5 bpm (-7 to -3 bpm, I2 = 88.3%). Older adults were less likely to be febrile (RR 0.89, 0.83 to 0.95, I2 = 85.9%) with a mean difference in temperature of 0.14°C (-0.26 to -0.02°C, I2 = 94.6%). Most (129/132) studies were at high risk of bias.

Conclusions: Whilst differences in absolute values were small, there was consistency in the finding that older adults were less likely than younger adults to be tachycardic or febrile. As vital signs at presentation may prompt suspicion of infection, influencing investigations and treatment, special consideration for the possibility of infection in older patients with normal vital signs may be warranted.

Keywords: age; diagnosis; infection; older people; systematic review; vital signs.

Figure 1

Flow chart showing the process for identification of studies eligible for inclusion.

Figure 2

(A) Meta-regression showing how proportion of patients with tachycardia changes with age; n = 22 studies (37 762 patients), slope coefficient −0.0095, 95% CI −0.02 to 0.00075, P = .069. (B) Meta-regression showing how admission HR changes with age; n = 30 studies (22 770 patients), slope coefficient −0.19, 95% CI −0.28 to −0.11, P < .05. (C) Forest plot of the risk ratio of tachycardia in older and younger patients; n = 13 studies, RR 0.82, 0.69 to 0.97, I² = 86.5%. (D) Forest plot of the mean difference in admission HR between older and younger patients; n = 11 studies, MD −5 bpm, −7 to −3 bpm, I² = 88.3%.

Figure 3

(A) Meta-regression showing how proportion of patients with fever changes with age; n = 58 studies (38 696 patients), slope coefficient −0.014, 95% CI −0.024 to −0.005, P < .05. (B) Meta-regression showing how admission temperature changes with age; n = 31 studies (21 566 patients), slope coefficient −0.0071, 95% CI −0.011 to −0.0027, P < .05. (C) Forest plot of the risk ratio of fever in older and younger patients; n = 19 studies, RR 0.89, 0.83 to 0.95, I² = 85.9%. (D) Forest plot of the mean difference in admission temperature between older and younger patients; n = 17 studies, MD −0.14°C, −0.26 to −0.02°C, I² = 94.6%.

Figure 4

(A) Meta-regression showing how proportion of patients with tachypnoea changes with age; n = 20 studies (31 748 patients), slope coefficient 0.032, 95% CI 0.03–0.034, P < .05. (B) Meta-regression showing how admission RR changes with age; n = 16 studies (11 985 patients), slope coefficient 0.04, 95% CI 0.0084 to 0.072, P < .05. (C) Forest plot of the risk ratio of tachypnoea in older and younger patients; n = 7 studies, RR 1.53, 1.2 to 1.96, I² = 86.6%. (D) Forest plot of the mean difference in admission RR between older and younger patients; n = 6 studies, MD 1 bpm, 0–2 bpm, I² = 87.1%.