Elsevier

Journal of Infection

Volume 68, Issue 4, April 2014, Pages 378-386
Journal of Infection

Temporal trends in incidence rates of herpes zoster among patients treated in primary care centers in Madrid (Spain), 2005–2012

https://doi.org/10.1016/j.jinf.2013.09.035Get rights and content

Summary

Objectives

This study aimed to estimate total and age-specific incidence rates of HZ with data from electronic clinical records in primary care (ECRPC) and to analyze trends by sex and age.

Methods

Descriptive cross-sectional study covering the incident HZ episodes registered in the ECRPC of the Madrid Regional Public Health System in 2005–2012. Annual crude and age-adjusted incidence rates were calculated. Differences by sex and age were assessed by poisson regression. The annual percentage of change (APC) of incidence rates and ‘breakthrough points’ of the time trends were determined with the Joinpoint Regression Program.

Results

211,650 episodes of HZ were identified (60.6% women, 52.2% > 55 years). The incidence rate increased from 363.21 to 481.92 per 100,000 person-year in 2005–2012. Rates were higher among women and increased with age. The APC for the period was 3.59% in men and 3.67% in women (p < 0.05). Age-specific rates increased in patients over 14 years. The APC in the 25–44 age group was 7.4% since 2007. The incidence rate ratio (women/men) was highest in this group.

Conclusions

The incidence of HZ presents an upward trend in 2005–2012 in adults and the elderly. Monitoring the incidence and age-specific rates, will help to detect changes in trends.

Introduction

Herpes zoster (HZ) results from the reactivation of latent varicella zoster virus (VZV). The triggers for reactivation of VZV have not been identified and probably involve multiple factors. However, specific components of cell-mediated immunity (CMI) have an important role in controlling the development of zoster by preventing reactivation within the neuron or the full clinical expression of reactivated VZV as zoster. The effectiveness of these protective components of CMI is well maintained in immunocompetent persons during childhood and early adulthood. These CMI components are believed to be partially or substantially maintained by periodic immunologic boosting.1

A recent literature review of population-based studies of HZ incidence in Europe published between 1960 and 2010, showed similar HZ incidence across the included countries for which data was available.2 Overall annual incidence varied from 2.0 to 4.6/1000 person-years depending on the country,2 which is consistent with previous published estimates.3 The lifetime risk of zoster is estimated to be 10–30% and incidence increases markedly with age, affecting up to 50% of people who live to 85 years.4, 5 The risk approximately doubles for each decade after 50 years of age.6 This age-related increase in HZ is due to a varicella zoster virus-specific decline in CMI with increasing age.7 About 5–18% of persons with HZ develop post-herpetic neuralgia, a disabling pain syndrome that can last months or even years with no consistently effective treatments.8, 9, 10 HZ imposes a significant burden of hospitalizations and results in large cost expenses, especially in population older than 50 years of age, with an annual hospitalization rate of 10.0 per 100,000 habitants and an average cost per hospitalization of more than 3500 €.11, 12

It has been speculated that a universal varicella vaccination program might alter the epidemiology of HZ due to the expected decline of the boosting of CMI caused by the reduced varicella circulation.13 The mechanism of exogenous boosting exists, although not for all persons, nor in all situations.14 Studies modeling the impact of a varicella vaccination program have predicted that cases of zoster may significantly increase in the first 50 years following vaccination.15, 16, 17 However, other model-based evaluations show that, after varicella immunization, an increase of HZ incidence is not a certainty. Rather, it depends on the presence or absence of factors promoting a strong boosting intensity, which may or may not be heavily affected by changes in varicella circulation due to mass immunization.18 In 2006 the Madrid Autonomous Region included universal varicella vaccination in its systematic vaccination schedule for children aged 15 months.19

The objectives of this study were to estimate total and age-specific incidence rates of herpes zoster on the basis of data drawn from electronic clinical records in primary care (ECRPC), and to analyze their temporal trends by sex and age.

Section snippets

Materials and methods

We performed a descriptive cross-sectional study covering all the HZ episodes registered in the ECRPC of the Madrid Regional Public Health System (MRPHS) for the period 2005–2012.

The target study population was defined as all persons included in the MRPHS, and therefore registered in the Individualized Health Card (IHC) database, from 1st January 2005 to 31st December 2012. IHC coverage was close to 95% of the population.

Health care data were drawn from ECRPC, implemented for 99% of primary

Results

Between 2005 and 2012, a total of 211,650 episodes of HZ were attended and registered in ECRPC in the Madrid Autonomous Region (Table 1). Of those, 60.6% were in women, and 52.2% were in patients older than 55 years old (n = 110,398). The mean age was higher in women (53.9 -SD 22.0- vs. 49.2 -SD 23.0-, p < 0.001). The distribution of these characteristics remained stable throughout the study period, with an increasing number of episodes over time.

The incidence rate of episodes of herpes zoster

Discussion

This study shows that HZ cases have been increasing, with a significant rise in annual incidence rates in Madrid from 2005 to 2012. This growing trend affected both sexes from age 14. This is the first study in our country to analyze temporal trends of herpes zoster attended in primary care using population-wide information. The large volume of data allows a detailed analysis of trends by age and sex.

More than a half of HZ episodes occurred in women and in people of 55 years and older.

Conclusions

The incidence of herpes zoster treated in primary care presents a clear upward trend in the period 2005–2012, especially in adults and the elderly. Women and the elderly are the most vulnerable to this disease. Data from ECRPC seem to be a valuable source of information for the surveillance of herpes zoster. Monitoring the incidence rates, and especially the age-specific rates, will help to detect future changes in HZ trends. It will be necessary to deepen the knowledge of other risk factors to

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