Objective To estimate incidence of Kawasaki disease (KD) over time among children in the city of Chandigarh, North India.
Patients and methods We analysed records of all children with KD below 15 years of age at the Pediatric Allergy Immunology Unit, Advanced Pediatrics Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, from January 1994 to December 2008. Diagnosis and treatment of KD were based on American Heart Association criteria. Among these cases, children residing in Chandigarh were identified. Yearly incidence was calculated and compared from 1994 to 2008.
Results During this period, 196 children were diagnosed as KD. Of these, 80 (40.8%; 48 boys, 32 girls) resided in Chandigarh. Four among these had coronary artery abnormalities (CAA) on echocardiography, while two had mitral regurgitation. Comparison of yearly data revealed increasing incidence of disease from 0.51 cases in 1994 to 4.54 cases per 100 000 children below 15 years of age in 2007. Majority (93.7%) of cases occurred in children ≤10 years of age with the highest incidence reported in the seventh year of life. Monthly distribution of disease showed two peaks with a maximum number of cases presenting in October followed by a second peak in May with a nadir in the month of February.
Conclusion Increasing incidence of KD in Chandigarh could be due to increasing clinical recognition as a result of greater awareness among paediatricians in the city, or may represent an actual increase in numbers. Striking differences from KD series reported from other countries include the older median age of our patients, low rate of CAA and a different bimodal seasonality, which may be epidemiologic clues to the nature of this vasculitis.
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Kawasaki disease (KD) is the leading cause of acquired heart disease among children in developed countries.1 2 Although there have been an increasing number of reports on KD from India over the last decade, little is known about the epidemiology of KD in our country.3,–,9 The incidence of KD in different countries varies widely with an incidence of 174 per 100 000 children <5 years of age in Japan, the country of highest incidence.1 10,–,20 Similar information on the Indian population is lacking. We, therefore, tried to ascertain the incidence of KD among children inhabiting the city of Chandigarh, North India, and examined trends in the distribution of the disease over a 15-year period (1994–2008).
What is already known on this topic
Epidemiology data pertaining to Kawasaki disease (KD) are available from Japan, North America and some of the European countries. KD is now the commonest cause of acquired heart disease in children in the developed countries. Very little is known about the epidemiology of KD from developing countries.
What this study adds
Epidemiological data on Kawasaki disease (KD) from the city of Chandigarh, North India, suggest that the incidence of KD is showing an upward trend. This may have implications for the future.
Patients and methods
The Post Graduate Institute of Medical Education and Research, Chandigarh, serves as a tertiary level referral centre for several northern Indian states and is the only tertiary level teaching hospital in Chandigarh. A retrospective review of records of the Pediatric Allergy Immunology Unit, Advanced Pediatrics Centre from 1 January 1994 to 31 December 2008 was performed. A total of 196 children (boys 68.9%, girls 31.1%) were identified to have KD. Diagnosis of KD was based on the American Heart Association criteria.21 Standard treatment protocols (ie, intravenous immunoglobulin (IVIG) and aspirin) were used for management. The children were evaluated by 2-D echocardiography during the acute and subacute stages of the disease.22 Cases were reviewed for age, sex, place of residence, date of admission, medical history and examination findings.
The city of Chandigarh has a population of 900 635 (rural 10.2% and urban 89.8%) with a decadal (1991–2001) population growth rate of 40.33%. Demographic data on all children below 15 years of age during the 15-year period (1994–2008) were obtained from detailed population databases maintained by the Census Department of India. As the population census is carried out for every 10 years, projections for intervening years were obtained from 2001 data by using the decadal growth rate (40.33%) reported for Chandigarh from 1991 to 2001.
As per our departmental norms, this manuscript was approved by the Publication Committee which consists of the Head of the Department and four faculty members.
The age-specific incidence of KD in Chandigarh during 1994 to 2008 was obtained by using the incident cases in each age group as the numerator and the population in each age group (0–14 years) calculated from census of 2001 as the denominator. We chose to express KD rates per 100 000 children less than 15 years, rather than less than 5 years as is customary in other countries, as the median age of our patients was older. Date of admission was used to determine the monthly distribution of KD cases in Chandigarh from 1994 to 2008.
Annual KD incidence
During the study period, a total of 196 children (boys 68.9%; girls 31.1%) were diagnosed to have KD. Eighty (boys 48; girls 32) among the 196 children were residents of the city of Chandigarh and were used for the rest of our analyses. Majority of patients belonged to the middle socio-economic status.
Since 1994, the annual incidence progressively increased with peaks observed every third to fourth year (figure 1). Comparison of yearly data revealed increasing incidence of the disease from 0.51 cases in 1994 to 4.54 cases per 100 000 children below 15 years of age in 2007. The trendline depicts an increasing incidence of KD cases in Chandigarh (figure 1) from 1994 to 2008. However, this increase was found to be inconsistent in nature.
Age- and sex-specific KD occurrence
The overall male to female ratio was 2:1 (figure 1). When the annual incidence was high, more cases among boys were observed. Of the 80 children, 6 (7.5%) were under 1 year of age while 35 (43.5%) were under 5 years. The median age was 5 years (6 years for boys, 4 years for girls; figure 2). Majority (93.7%) of cases were ≤10 years of age. Highest occurrence rates were seen in children around 7 years of age and those in the age group of 1–2 years. A rapid decline in incidence was noted after 10 years of age.
Monthly distribution of KD cases
The analysis of the monthly distribution of cases revealed a bimodal seasonality (figure 3) with peaks observed in October and again in May with lowest number of patients reported in February.
Of the 80 KD patients, 68 (85%) received IVIG as treatment during the acute stage. Four (5.8%) had coronary artery abnormalities on echocardiography, while two had mild mitral regurgitation. All four patients with coronary artery abnormalities had received treatment with IVIG. Intravenous methylprednisolone was not used as primary therapy in any of our patients.
KD is now the most common cause of acquired heart disease in children in Japan, Western Europe and North America.4 15 Similar data on the incidence of KD in developing countries are scarce.16,–,19 Our study is the first to attempt an estimate of the regional occurrence rates of KD in India. While rheumatic fever continues to be the leading cause of acquired heart disease among children in our country,23 our data suggest that the long-term consequences of KD may also assume importance in the years to come.
At Chandigarh we diagnosed our first KD patient in 1994.24 Since that time, the annual occurrence rates of KD in Chandigarh have shown a progressively increasing trend. This could be due to increasing clinical recognition as a result of greater awareness among paediatricians in the city or may represent an actual increase in numbers.25 Several studies have reported similar increase in KD cases over the years.26,–,28 Although it is theoretically possible that KD may have been misdiagnosed as measles and other viral exanthemata29 in the past, this is not likely because clinical experience suggests that the number of measles cases in Chandigarh has not significantly changed over the last 15 years. Measles vaccine coverage rates in our city have consistently remained upwards of 80% since the early 1990s.
Median age of our patients was 5 years (6 years for boys, 4 years for girls). This is much higher than comparable figures reported for both Japanese and Western populations.1 10,–,15 26,–,28 30 31 We do not have an adequate explanation for this but it may well represent genetic differences among populations. Though previous work has also suggested an older median age for KD patients in India, this is the first time that actual incidence data have substantiated this impression.8 25 32
The monthly distribution of KD cases revealed a striking bimodal seasonal variation which was consistent over the last 15 years. Peak occurrence rates were seen in the months of October (autumn season) and May (peak summer, with maximum daytime temperatures in the range of 43–46°C). These 2 months are also among the driest months of the year at Chandigarh having little or no rainfall. It is noteworthy that October has some of the most important Indian festivals (eg, Diwali and Dussehra) and represents a time when schools are closed for long periods and families often get together. This may possibly result in overcrowding at home. Schools also remain closed during the latter half of May for the summer vacations. In Chandigarh, the month of February represents the end of winter and the onset of spring with the temperatures ranging between 5–8°C (minimum) and 19–22°C (maximum). The schools, however, remain open throughout the month. In Japan, over a 14-year (1987–2000) period, the months of January/February and June/July had the highest incidence.33
The incidence of coronary artery abnormalities in our series is very low. Prior to 2002, echocardiography in children with KD at our centre was being performed on a routine basis by cardiologists specialising in adult medicine as there was no trained paediatric cardiologist. Since 2002, most of the echocardiograms have been performed by a paediatric cardiologist. The four patients with coronary artery abnormalities were all diagnosed after 2002. Other centres in India have also published low aneurysm rates compared to Japan and Western countries.34 35
We are aware of several limitations to our study. First, it is possible that some KD cases could have been diagnosed and managed at other hospitals and private health clinics in the city without being referred to our institute. Although possible, this number would be necessarily small because for a condition like KD (for which the costs of IVIG therapy are high), most parents residing in the city of Chandigarh would usually seek a second opinion from our institute which is the only tertiary level teaching hospital in the city. Another limitation pertains to the method used for estimating the rate of growth of population below 15 years of age for the intervening years between 1991 and 2001. As the census data are not available on a yearly basis, we have used projections based on the decadal growth rate (40.33%) reported for Chandigarh from 1991 to 2001. It can be argued that the growth rate for the population under 15 years of age may be different from the overall growth rate, but there were no other estimates on which to base our analysis. Finally, the small number of patients resulted in wide confidence limits for estimates of trends.
In summary, if the Chandigarh trends can be taken as representative for the country KD appears to be emerging as an important cause of acquired heart disease in children in India. As the incidence of rheumatic fever falls with better antimicrobial management of childhood streptococcal sore throat, KD may soon emerge as the leading cause of paediatric acquired heart disease in our country just as it has in the developed countries. Regional genetic differences across India require that prospective studies of KD incidence be conducted at different locations across the country to develop a more accurate snapshot of KD incidence and outcome in Indian children.
Funding The contribution of JCB was supported in part by a grant from the National Institutes of Health, Heart, Lung, Blood Institute (K24 HL-074864 to JCB).
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
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