The Incidence of Diabetes in Scottish Children
Thursday, 02 March 2017
From 1900 to 2100
Professor Norman Waugh, Professor of Public Health Medicine & Health Technology Assessment, Warwick Medical School
"The Incidence of Diabetes in Scottish Children"
Norman Waugh (MBChB Edinburgh, DA, MRCP(UK), MPH, FFPH) is a part-time professor of public health medicine and health technology assessment in Warwick Medical School, and emeritus professor in Aberdeen. He was consultant in PHM in Grampian Health Board from 1993-1999, and professor of public health medicine in University of Aberdeen from 2003 till retirement in 2010. He is a member and former chair of the Scottish Study Group for the Care of Diabetes in the Young, and was curator of the SSGCDY register for many years.
His main activities in the last 20 years have been in health technology assessment, including trials. He is deputy chief investigator of the REPOSE trial of insulin pumps, and is also involved in trials in diabetic eye disease. His research interest has mainly been in diabetes, ranging from epidemiology to HTA, and he has led most of the technology assessment reports to support the work of policy-makers including NICE and the National Screening Committee.
The SSGCDY register has been used for monitoring incidence and outcomes. The incidence of type 1 diabetes in Scottish children is one of the highest in the world. This presentation will look back at trends in incidence and at variations within Scotland.
- The President welcomed the company to the meeting, the first to be held in the refurbished Hall. She explained that the paintings from the Hall were currently in storage while new exhibition locations – perhaps some in the Suttie Building – were arranged.
- Dr James Henderson was then invited to speak, having asked to do so immediately prior to the meeting. He read a short statement to the effect that some senior members of the Society wished to exercise their constitutional right to ask for an extraordinary meeting of the membership to be called to discuss the current status and future of the Society. The President immediately agreed to the request but, having had no prior notification of this declaration, was not in a position to give any immediate arrangements; she said the hope would be to hold the meeting within the next two months. Dr White later intimated that as May was busy with Society engagements, April would be a better time. This, of course, falls within the President’s suggested 2 month window.
- The President informed the company that the slide show playing as the meeting gathered was of pictures taken at the Burns event held jointly with the AU Med Soc in January.
- The Ashley Mackintosh Golf Cup was finally presented to the 2016 winners Chris Driver and Doug Wardlaw. An announcement about the 2017 competition has just been sent out to the membership.
- The meeting was reminded of the additional events in this year’s programme: 6th May : Famous for Five Minutes Charity Concert; 18th May : Heritage evening; 25th May : Electives evening.
- Members were also reminded that a request had been sent out for nominations for a) President Elect 2017-8 and b) President’s Medal 2017 and that both lists are still open.
Dr Foster then introduced the evening’s main speaker - Professor Norman Waugh who is now Professor of Public Medicine and Health Technology Assessment at Warwick Medical School. He was formerly an NHS Consultant in Public Health in Grampian and from 2003 until his retirement from full-time work in 2010, he held the post of Professor of Public Health Medicine with the University of Aberdeen. He is a member and former chair of the Scottish Study Group for the Care of Diabetes in the Young and was curator of that group’s childhood diabetes register for many years. This has been used for monitoring incidence and outcomes of childhood diabetes for over three decades In Scotland where the incidence of type 1 diabetes in children is among the highest in the world. He has a longstanding interest in Health Technology Assessment and in research into many aspects of diabetes epidemiology and service provision. He has led many technology assessment reports on diabetes supporting the work of policy makers such as NICE and the National Screening Committee.
Professor Waugh then gave his talk entitled, ‘The Incidence of Diabetes in Scottish Children’.
The account began with reports of the realisation in Glasgow and then in Edinburgh in the late 1970s that the number of new presentations of Type 1 diabetes in children in Scotland was rising rapidly, showing up to a five-fold increase in incidence over a period of 20-30 years. Early attempts to measure the true incidence of diabetes through the 20th century had several methodological barriers to overcome, including the fact of the need to include figures from residential care homes due to the significant number of children who had apparently been taken into care in the belief that this was the only way their Type 1 diabetes could be effectively managed! Childhood type 1 diabetes prevalence rose from 35 per 105 (1961) to 150 (1997) and 220 (2014).
In the early 1980s, the Scottish Study Group for the Care of Diabetes in the Young (originally named the SSG for the Care of Young Diabetics) was established, involving representation from all regions of Scotland, to encourage research and sharing of information and experience. Shortly after its formation, the Group established a register which would be used to gather comprehensive information on new cases of childhood diabetes from the whole of the country and since then a near-complete picture has been prospectively collected. Between 1984 and 2000 there was a steady rise in incidence of about 2% per year reaching 24 per 105 per year. There is perhaps a suggestion in the newest data that this is beginning to reach a plateau in Scotland as has already seen in Norway.
Two regional epidemiological analyses in the early 80’s hinted at higher incidence of childhood diabetes in more affluent populations, in rural populations, in first born children, with higher maternal age and following Caesarean section. The SSG register also showed some geographical variations across Scotland, with highest rates in Highland and the Northern and Western Isles whereas the lowest rates were seen in Glasgow, Edinburgh and Borders. While refinement of classification criteria defined and hence differentiated between ‘remote’ and ‘rural’ descriptors, a Cochrane review of urban to rural childhood diabetes incidence showed conflicting results in different countries with some having higher rural and others having higher urban incidences.
On arrival in Aberdeen to take over the Paediatric Diabetes service at the start of the 1980s, Dr Peter Smail had conducted a study of historical records on the incidence of childhood diabetes in the North-East showing fairly steady, and low, incidence rates from 1920s – 40s but then a sharp rise from mid to late 50’s. These figures were revisited in 2005 when a more detailed epidemiological analysis was undertaken by examining archived records, hospital admission registers and even a poster campaign within diabetes clinics seeking contact from Type 1 diabetes patients diagnosed in childhood between 1920 and 1960. This study showed that there had been very few inaccuracies in Dr Smail’s analysis thus vindicating, as far as reasonably possible, the conclusion that childhood diabetes incidence had indeed been low for several decades before the significant rise. Similar findings from Scandinavia also reflected low incidence around the same years as in Scotland – and thus failure of ascertainment (including, e.g. early deaths in ketoacidosis) seems to be an unlikely cause of the previously documented low incidence.
Studies continued to show an association between rural populations and Type 1 childhood diabetes but a study from Aberdeen no longer seemed to show increased risk with higher maternal age. The growing evidence, however, showed a definite increase in incidence, a male preponderance among cases, an earlier age of onset of childhood diabetes (by an average 7 months), with higher numbers in the North and in more affluent populations.
In considering possible contributory factors to the pathogenesis of Type 1 diabetes, Professor Waugh described a serendipitous involvement in a research study looking to see whether the levels of the protein, calprotectin, in faecal samples could usefully distinguish between inflammatory bowel disease and irritable bowel syndrome. This facilitated awareness of data showing that the incidence of Crohn’s disease, like Type 1 diabetes, had been increasing over time and had a male preponderance. Further investigation revealed another study showing, in addition, that Crohn’s disease incidence was higher in the north and lower in less affluent populations. This raised the possibility of a potential overlap in some of the (still unknown) triggering factors for each condition. Attention to asthma epidemiology looking for further linkage was short-lived as asthma incidence had risen and fallen again while diabetes and Crohn’s continued to rise.
Reference was then made to the work of Graham Rook on the Hygeine or ‘Old Friends’ hypothesis. Which suggests that reduced early childhood exposure to various infectious, and perhaps commensal, microorganisms and/or parasites could impair the natural development of the immune system; the relevant corollary for conditions with an autoimmune pathogenesis, such as Type 1 diabetes, being a subsequent increase in susceptibility due to defective immune tolerance. The social, environmental and health care changes that prevailed after World War II would certainly be compatible with a change in exposure to ‘germs’. Also, some laboratory experiments have offered support for this hypothesis with pinworm infection, for example, having been shown to protect mice form experimentally induced Type 1 diabetes. [Professor Waugh, at this point, drew attention to Diapedia (www.diapedia.org) an ‘open-access, peer-reviewed, unbiased, up-to-date knowledge base of diabetes information’ where further data on the Hygiene Hypothesis could be found.
A natural extension of the Hygiene hypothesis was to study changes in prevalence of tuberculosis to see whether there were any potential associations with type 1 diabetes epidemiology. Data were shown on the significant reduction in childhood mortality in Aberdeen through the first half of the 20th Century. Deaths attributed to tuberculosis among children fell from around 45 per year to 2 per year over the period 1900-45. So the impact of tuberculosis was falling long before the observed rise in Type 1 diabetes incidence and, despite the finding that BCG can protect mice from experimental diabetes, it does not appear that there is an important link between falling tuberculosis and increasing diabetes rates.
Seasonal variations in presentation of childhood diabetes have also been studied with higher rates in the winter months. Interestingly this is mostly due to numbers in older children since, before the age of 5, there is no seasonal variation. This type of observation adds to the improbability of fully unravelling diabetes susceptibility from epidemiological studies as it suggest the likelihood of complex interrelationships between different innate and environmental susceptibilities that do not necessarily produce a consistent impact i.e. there may be different subgroups within diabetes patient populations having different susceptibility to different putative pathogenic exposures. Furthermore, the limited overall value of genotype as a predictor of diabetes susceptibility is shown by the relatively low incidence of Type 1 diabetes in the children of parents with the same condition, currently quoted at 30 years of age in children of a T1DM mother (2%) or father (6%).
So while many studies have raised potential indications of factors responsible for causing Type 1 diabetes, or indeed protecting against its development, a situation prevails in which there is still nothing proven, at least in any clinically useful way. The question thus arises as to whether epidemiology can make any further contribution to the reasons behind the development of Type 1 diabetes in childhood, and whether it has finally failed to produce any useful applications to the prevention of the condition. The low absolute incidence of childhood diabetes means it is effectively impossible to adequately power prospective studies of any relatively ‘low-impact’ contributory factor. The potential for influential risk factors changing over time, and possible complex interactions of different environmental and/or genetic influences perhaps signal that the only epidemiological way forward is to try to develop a ‘whole life-course’ study model.
In summary, investigation to date confirms that childhood diabetes in Scotland was rare before the 1950s, has shown a marked rise in incidence 1960-2010 (perhaps now reaching a plateau), occurs on average 7 months earlier than formerly, is commoner in the north and presents (in older children) more commonly in the winter. A potential relationship with low vitamin D synthesis in Scottish winters is a recent addition to the list of possible associations but the fact is that currently the ‘cause’ of childhood diabetes is unknown. The rise in the last 50+ years is, however, mainly due to a combination of several/many environmental factors: harmful ones added, good ones removed, or a combination of both.
Professor Waugh concluded by acknowledging the work of colleagues who had contributed to the various studies and, in particular, to the maintenance of the Scottish childhood diabetes register, particularly Fred Nimmo and Chris Paterson with whom he had worked while in Aberdeen. He also paid tribute to the work of Aileen McKillop-Smith, Senior Dietitian with NHS Grampian, (who was in the audience), who had for years maintained the register; she was credited with the observation that patients who successfully commenced insulin pump therapy made similar favourable comments (and achieved similar improvements in their blood glucose results) to those who had undergone intensive educational interventions such as the DAFNE course. This has led on to the multicentre REPOSE trial in which Professor Waugh is Deputy Chief Investigator. This ongoing study in Type 1 diabetes is a randomised evaluation of intensive education plus multi-dose insulin injections versus insulin pump therapy.
There followed a short question and answer sessions including topics such as the potential validity and reasons behind the possible plateau in incidence, the consistent failure of trials of immunosuppressant therapy administered early after diagnosis of Type 1 diabetes and the possible effects of intrauterine influences on susceptibility to the condition. The President gave a vote of thanks and the meeting closed.