European Heart Journal Advance Access published February 14 2006 European Heart Journal doi 10 1093 eurheartj ehi707 Clinical research Incidence of recognized and unrecognized myocardial infarction in men and women aged 55 and older the Rotterdam Study Anneke de Torbal Eric Boersma Jan A Kors Gerard van Herpen Jaap W Deckers Deirdre A M van der Kuip Bruno H Stricker Albert Hofman and Jacqueline C M Witteman Department of Epidemiology and Biostatistics Erasmus MC PO Box 1738 3000 DR Rotterdam The Netherlands Received 12 April 2005 revised 31 October 2005 accepted 8 December 2005 KEYWORDS Myocardial infarction Electrocardiogram Elderly Incidence Aims Contemporary data on the incidence of unrecognized myocardial infarction MI among subjects aged 55 and older are limited Methods and results We studied the incidence of recognized and unrecognized MI in the Rotterdam Study a population based cohort of men and women aged 55 and older The baseline examination was performed during 1990 93 with follow up examinations during 1994 95 and 1997 2000 Baseline and follow up 12 lead ECGs were analysed by the Modular ECG Analysis System The 5148 participants who had no evidence of prevalent infarction were the subjects for analysis Incident recognized infarction was defined as the occurrence of a fatal or non fatal event coded as I21 according to the International Classification of Diseases 10th edition A repeat ECG was available in 4187 subjects An unrecognized infarction was considered to have occurred if there was electrocardiographic evidence in the absence of a clinically recognized event During a median follow up of 6 4 years 141 incident recognized infarctions occurred and the incidence rate of this event was 5 0 per 1000 person years The incidence was higher in men 8 4 than in women 3 1 The incidence rate of unrecognized infarction was 3 8 per 1000 person years Men 4 2 and women 3 6 had approximately similar incidence Hence the proportion of unrecognized infarction was lower in men 33 than in women 54 This difference in proportion of unrecognized infarctions was independent of age Conclusion A high proportion of incident MIs remains clinically unrecognized As a history of MI is associated with an increased risk of repeat cardiovascular complications our data suggest a need for periodical electrocardiographic screening to recognize prevalent infarctions and to install effective preventive treatment in those aged 55 and older Introduction During the last decades ischaemic heart disease mortality has considerably decreased in most countries belonging to the Western world 1 2 Changing coronary event rates is the major determinant of this decline whereas improved coronary care and secondary prevention were responsible for decreased event rates 3 4 Despite these promising developments ischaemic heart diseases will remain a major health issue during the decades ahead for several reasons First ischaemic heart diseases will persist to occur at early ages in individuals with a genetic predisposition and in those with an unfavourable clinical risk profile Furthermore survivors of an acute coronary syndrome constitute a population with chronic cardiac conditions and remain at increased risk of future fatal and non fatal cardiac events In addition evidence exists that patients and doctors fail to adequately put effective preventive Corresponding author Tel 31 10 408 8190 fax 31 10 408 9382 E mail address j witteman erasmusmc nl measures into practice 5 Last but not the least it should be realized that the Western world is ageing and heart diseases come with age This latter observation has been the keynote behind the Rotterdam Study a long term prospective cohort study in men and women aged 55 and older 6 on which we report Myocardial infarction MI is the most dominant manifestation of ischaemic heart diseases Although MI is usually associated with severe symptoms several cohort studies have indicated that up to 44 of the events remain clinically unrecognized until routine and repeated imaging of the cardiac function is performed 7 These unrecognized or silent MIs should not be considered minor events In fact it has been repeatedly demonstrated that patients with prevalent unrecognized MI have similar prognosis as those with prevalent recognized infarction 8 10 Contemporary data on the incidence of unrecognized MI among subjects aged 55 and older in the general population are limited Most epidemiological studies were conducted before the 1990s had an upper age limit or enrolled patients with established coronary disease 11 20 In addition The European Society of Cardiology 2006 All rights reserved For Permissions please e mail journals permissions oxfordjournals org Page 2 of 8 contradictory results have been reported with some studies suggesting a steadily increasing incidence with age12 17 and others reporting a stabilizing or even decreasing incidence in individuals over the age of 70 8 16 These differences were probably confounded by gender differences between the studied cohorts Against this background we studied the incidence of recognized and unrecognized MI in the Rotterdam Study population We were especially interested to learn to what extent the incidence of recognized and unrecognized MI increased with age and if so whether or not differences were apparent between men and women Methods The Rotterdam Study The Rotterdam Study is a prospective population based cohort study of 7983 men and women aged 55 and older Its overall aim is to investigate the incidence and determinants of chronic disabling diseases From 1990 to 1993 all inhabitants of a suburb of the city of Rotterdam aged 55 and older were invited to participate in the study The overall response rate was 78 A trained investigator visited all participants at home and collected information using a computerized questionnaire The obtained information included current health status medical history drug use and smoking behaviour Additionally during two visits to the research centre established cardiovascular risk factors were measured The Medical Ethics Committee of the Erasmus MC approved the Rotterdam Study and written informed consent was obtained from all participants A more detailed description of the Rotterdam Study and the collection of data have been given elsewhere 6 Study population A total of 7085 participants visited the Rotterdam Study research centre shortly after the enrolment interview Living in a nursing home or limited
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