Elsevier

The Lancet

Volume 352, Issue 9145, 19–26 December 1998, Pages 1970-1973
The Lancet

Articles
Age-specific incidence and prevalence rates of treated epilepsy in an unselected population of 2 052 922 and age-specific fertility rates of women with epilepsy

https://doi.org/10.1016/S0140-6736(98)04512-7Get rights and content

Summary

Background

There are no data on prevalence or incidence of treated epilepsy, and no data on fertility of women with epilepsy from an unselected UK population.

Methods

We used the General Practice Research Database to ascertain the incidence and prevalence of people with treated epilepsy in an unselected population of 2 052 922 people in England and Wales, and also age-specific fertility rates. We defined period prevalence of treated epilepsy as the number of people with epilepsy taking an antiepileptic drug per 100 000 people during 1995. The incidence of treated epilepsy was defined as the number of new cases of treated epilepsy per 100 000 people during the same period. We calculated fertility rates among women with treated epilepsy between 1991 and 1995 and compared these rates with the population rates for England and Wales in 1993.

Findings

The period prevalence of treated epilepsy in 1995 was 5·15 per 1000 people (95% CI 5·05–5·25). The prevalence was lower in children (age 5–9 years 3·16 [2·86–3·48]; 10–14 years 4·05 [3·70–4·42]), and higher in older people (65–69 years 6·01 [5·50–6·57]; 70–74 years 6·53 [5·97–7·14]; 75–79 years 7·39 [6·73–8·11]); 80–84 years 7·54 [6·78–8·39]; 85 years and older 7·73 [6·98–8·66]). The incidence of treated epilepsy was 80·8 per 100 000 people (76·9–84·7). The incidence was lower in children (5–9 years 63·2 [50·5–79·1]; 10–14 years 53·8 [42·4–68·3]) and higher in older people (65–69 years 85·9 [68·5–107·3]; 70–74 years 82·8 [65·0–105·2]; 75–79 years 114·5 [116·9–179·2]; 80–84 years 159 [125·2–202·6]; ⩾85 years 135·4 [100·4–178·7]). Fertility was lower among women with treated epilepsy, with an overall rate of 47·1 livebirths per 1000 women aged 15–44 per year (42·3–52·2), compared with a national rate of 62·6 in the same age-group. The standardised fertility ratios were significantly lower between the ages of 25 and 39 years in women with epilepsy (p<0·001).

Interpretation

Compared with previous studies, we found that the incidence of epilepsy was higher in elderly people and lower in children. The prevalence rates also increase with age. Women aged 25–39 years with treated epilepsy have significantly lower fertility rates than those in the general population. Research is needed to identify any potentially preventable causes for the low fertility rates.

Introduction

Over 99% of people in the UK are registered with a general practitioner, which provides an opportunity to gather epidemiological data on the health and morbidity of unselected populations of patients. A knowledge of the incidence and prevalence of any disease is important for planning medical services. The Office for National Statistics' General Practice Research Database (GPRD) holds anonymous records of 3·6 million patients from more than 500 general practices in England and Wales, which represents over 6% of the total population of England and Wales.1, 2 The GPRD is an unrivalled source of continuous data on the diagnosis and treatment of illness in general practice, and has been extensively validated.1 We used this database to report the age-specific period prevalence and incidence rates of treated epilepsy in 2 052 922 people, and the age-specific fertility rates in 1991–95 of women with treated epilepsy. Our study is the largest on incidence and prevalence of treated epilepsy reported to date in the UK, and is the only contemporary population-based study to investigate fertility rates. We selected patients taking treatment since this population is the key group for rational planning of services for epilepsy.

Section snippets

Incidence and prevalence rates of treated epilepsy

Population and case ascertainment—We used data from 294 computerised general practices that entered complete data in the GRPD during the study year (1995). All regions in England and Wales were represented. The database comprised 2 052 922 people with a similar age and sex distribution to that published in 1991 national census figures. We identified prevalent and incident cases of treated epilepsy in this population.

We defined prevalent cases as all patients who had received a prescription for

Prevalence and incidence rates

Table 1 shows the incidence and period prevalence of treated epilepsy by 5-year age categories in 1995, and the raw data on which these figures are based; figure 1 shows the respective graphs for prevalence and incidence.

Fertility rates

Table 2 and Figure 2, Figure 3 show the fertility rates for women aged 15–44 years with epilepsy by age-groups compared with the rates for the general UK population, together with the age-specific standardised fertility ratios. There was a significant reduction in fertility

Discussion

Previous studies have reported data on overall rates of epilepsy in the UK, but none in a population of this large size, and few in which the treatment status has been reported.4 Incidence rates of epilepsy worldwide have varied between 11 and 190 per 100 000 people; most countries have rates of 40–80 per 100 000 people. The differences between countries can be largely accounted for by differences in methodology and definitions. Previous UK studies reported rates of 63, 52, and 48 per 100 000

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