The burden of diabetes in Ireland

Diabetes is the most challenging health problem of the 21st century due to its progressively increasing prevalence and associated complications; and type 2 diabetes is the main driver of this increase, accounting for nine in 10 of all cases.

Speaking at the Inaugural Conference of the National Clinical Programme for Diabetes in Farmleigh, Dublin, Prof Patricia Kearney, research professor at the department of epidemiology and public health in University College Cork, emphasised that diabetes is ‘truly a global problem, not just a problem of the developed world’.

She noted that throughout the world, diabetes ‘imposes a large economic burden on the individual and national healthcare systems’. Healthcare expenditure on diabetes accounted for 11% of the total healthcare expenditures in the world in 2011. This includes spending on diabetes by the health system, as well as by people living with the condition.

The disease now costs the State around €580 million per year and this figure is projected to increase significantly.

In 2013, Prof Kearney was one of six national recipients of the prestigious HRB Research Leader Award. In partnership with the National Clinical Programme in Diabetes, she and her colleagues are focusing on ‘Improving Care for People with Diabetes: A Population Approach to Prevention and Control’.

This research programme aims to measure the public health burden of diabetes in Ireland and evaluate the implementation of the National Clinical Programme in Diabetes. It also aims to model current and future diabetes care costs, and develop, implement and assess a lifestyle intervention in women at risk of gestational diabetes.

As part of this, Prof Kearney carried out a systematic review of the prevalence and complications of diabetes in Ireland between 1998 and 2013, which had been reported in a number of studies.

She wanted to create a comprehensive understanding of the situation in Ireland and identify possible gaps in the evidence base to inform the ongoing research programme.

Those involved had to be 18 years or older and people with type 1 diabetes were excluded.

Following extensive searches, 1,368 articles and four reports were identified. After duplicates were removed, 1,135 articles were left. After screening and eligibility was taken into account, 17 articles and four reports were considered appropriate to be included in the systematic review.

From these, Prof Kearney looked at microvascular and macrovascular complications. Microvascular complications are retinopathy, neuropathy and nephropathy. Macrovascular complications are ischaemic heart disease, cerebrovascular disease and peripheral vascular disease.

Prof Kearney pointed out that people with diabetes have a two to six times higher risk of developing these complications compared with the general population.

Her analysis of the data revealed that prevalence estimates of these complications varied depending on the population, the way the study had been designed and the definition of diabetes that had been used. 

However overall, there was ‘limited information available on the current prevalence of microvascular and macrovascular complications’.

In order to tackle this, Prof Kearney decided to focus on the prevalence of type 2 diabetes and related complications in Ireland. To estimate this, she used the Irish Longitudinal Study on Ageing (TILDA). This is a nationally representative survey of the Irish population aged 50 and over and their spouses or partners.

Using this study, Prof Kearney also wanted to determine the prevalence of microvascular and macrovascular complications in Irish people with type 2 diabetes and assess the factors associated with these complications.

She carried out a cross-sectional analysis of the first wave of TILDA participants aged 50 or older. This involved computer-assisted personal interviews and health assessments undertaken by trained study nurses.

She focused on people with a diagnosis of type 2 diabetes who had either self-reported a doctor diagnosis of the condition, or reported use of medication such as insulin. She also looked at microvascular and macrovascular complications.

Other areas of interest included the age of the participants at the time of their diagnosis, their use of medication and previous diagnoses of hypertension or high cholesterol.

Assessing the prevalence of type 2 diabetes, Prof Kearney found that 8,175 participants were available for analysis, 655 of whom had type 2 diabetes. The prevalence of type 2 diabetes was therefore 8.5%. Among those aged 50-64, the prevalence was 6.3%, among those aged 65-74, the prevalence was 11.4% and among those aged 75 or older, the prevalence was 11.9%.

A higher prevalence was found in men (10.3%) compared to women (6.8%).

Prof Kearney found some interesting characteristics of the TILDA population when stratified by diabetes. For example, TILDA participants with type 2 diabetes were less likely to have private health insurance and more likely to have State assistance.

Altogether, just under 50% of participants with type 2 diabetes had State-assisted medical cover, compared to just under 35% of the general population. And while 38% of the general population had private insurance, among those with type 2 diabetes, this fell to 23%.

When it came to education, 43% of the general population had completed secondary school and 19% had a third level education. Among those with type 2 diabetes, 36% had completed secondary school and 12% had a third level education. 

There was little difference in smoking levels, with 20% of the general population currently smoking compared to just under 19% of people with type 2 diabetes.

However those in the general population did appear to be more physically active than those in the diabetes population. While similar numbers in both populations undertook moderate exercise, 34% of the general population said they undertook high intensity physical activity compared to 21% of the diabetes population.

People with type 2 diabetes were also much more likely to have been medically diagnosed with hypertension and high cholesterol.

Some 62% of those with type 2 diabetes had hypertension compared to 35% of the general population, while 51% of those with type 2 diabetes had high cholesterol compared to 36% of the general population.

BMI was also an area with major differences. Just 7% of people with type 2 diabetes were considered to be a normal weight compared to 23% of the general population. 

While more people in the general population were overweight than in the diabetes population – 43% versus 33% - just under 60% of those with diabetes were found to be obese compared to 33% of the general population.

Prof Kearney then looked specifically at the prevalence of microvascular and macrovascular complications among those with self-reported diabetes – 364 males and 260 females.

More than one in four were found to have at least one microvascular complication. The most prevalent was neuropathy (14.6%), followed by retinopathy (8.2%), proteinuria (6.4%), kidney damage (5.1%) and leg ulcer (4.3%).

When it came to macrovascular complications, just over one in 10 women and one in six men were found to be affected. The most common macrovascular complication overall was myocardial infarction at 9.3%. However, this was much more prevalent in men (13.2%) compared to women (3.9%).

Heart failure was also more common in men (5.2%) than women (1.1%). 

Stroke on the other hand was more common in women (4.1%) than men (2.3%), as was TIA (4.8% versus 2.5%).

Summarising her findings, Prof Kearney pointed out that this marks the first study to look at the prevalence of complications among adults in Ireland using nationally representative data.

It is clear that type 2 diabetes is common among older people in this country and there is a high burden of microvascular and macrovascular complications in this population, she stated.

It is hoped that these findings can contribute to the existing evidence in relation to the burden of diabetes and will be useful in planning the development of diabetes care in Ireland.

This could not come at a more important time because as Prof Kearney pointed out, ‘ageing has come later in Ireland and as this is an important factor in diabetes, we will see increases in diabetes soon that are linked to ageing’.