Professor Faculty of Health Sciences, McMaster University, Canada
Background: The lifetime risk of herpes zoster (HZ) is 1 in 3. HZ risk increases with age and is higher in immunocompromised individuals and those with chronic conditions such as cardiovascular disease (CVD). Emerging data suggest a bidirectional relationship between HZ and CVD; the risk of major adverse cardiac and cerebrovascular events was 19% higher in patients with HZ in the year following diagnosis versus matched controls. As a substantial proportion of Ontario residents have chronic conditions, including CVD, this study aimed to quantify HZ risk in this population.
METHODS AND RESULTS: A retrospective cohort study was conducted using adult near-census administrative medical records from the Institute for Clinical Evaluative Sciences (ICES) to capture healthcare visits and diagnoses. Incident HZ cases were captured over 11 years from April 1, 2011 to March 31, 2022. An all-history review of ICES data extended back to April 1, 2002 to ensure only the first HZ incidence was captured and to identify patients with chronic conditions, including CVD, based on specified diagnostic codes (Table 1). Patients with HZ were matched to respective controls without HZ (general population or with specific chronic conditions). Conditional logistic regression was used to calculate adjusted odds ratios (aOR) with 95% confidence intervals (CI) for outcomes of interest; reference groups were patients without the characteristic of interest.
Of the 617,352 patients with an incident diagnosis of HZ, 211,446 (34.25%) had CVD and 46,385 (7.51%) had cerebral vascular disease (CeVD). Compared with controls without chronic conditions, HZ risk was increased in patients with CVD (aOR 1.15 [95% CI 1.14–1.15]) or CeVD (aOR 1.01 [95% CI 1.00–1.02]). Among patients with CVD/CeVD, age-stratified HZ risk was highest in individuals aged ≥65 years and lowest in those 18–29 years (reference group: 50–64 years; Table 2A), consistent with immunosenescence. More broadly, patients with chronic conditions had higher HZ risk than those without (≥1 chronic condition: aOR 1.21 (95% CI 1.20–1.21); ≥2 chronic conditions: aOR 1.27 (95% CI: 1.26–1.28); Table 2B).
Conclusion: The risk of HZ increases with chronic conditions, including CVD/CeVD, and with age. This underscores the importance of continuous HZ risk assessment in routine clinical care of aging populations, disproportionately affected by CVD and CeVD. In Ontario, a large proportion of adults diagnosed with HZ had chronic conditions, such as CVD. Preventive strategies such as HZ vaccination could be considered to reduce HZ occurrence.
