Links between diabetes and depression are similar across Europe, study of over-50s in 18 countries finds

(Press-News.org) The relative increase in odds of an individual with diabetes developing severe symptoms of depression – and vice versa – is the same, regardless of where they live, a study of over-50s in 18 countries in Europe that is being presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Vienna, Austria (15-19 September) has found.

Individuals with depression are more likely to develop diabetes and vice versa.  In addition, previous research has shown that the strength of this association depends on the quality of diabetes care, with the links between diabetes and depression weaker in countries with good diabetes care.

For the new study funded by Ireland’s Health Research Board, Jaroslav Gottfried, of University College Dublin, Dublin, Ireland, and colleagues examined whether a wide range of country and individual-level factors, from wealth inequality in a country, to whether a person smokes, influence the association between diabetes and depression. For example, is someone with diabetes more likely to develop depression, and vice versa, if they also smoke?  Or does smoking not make a difference?

“Not everyone with diabetes will develop depression; and similarly, not everyone with depression will develop diabetes,” explains Dr Gottfried. “Greater knowledge of the factors that influence the association between diabetes and depression would make it easier to predict which people with diabetes are most likely to develop depression and vice versa.

“This would allow healthcare professionals and policymakers to then, for example, target medical and mental health care at the most vulnerable people with one of the conditions, in an effort to prevent them from developing the other condition.”

The country-level factors included quality of diabetes healthcare (Euro Diabetes Index 2014), diabetes-related expenditure (Eurostat), age-specific risk of poverty (Eurostat), gender inequality (Gender Inequality Index) and wealth inequality (Gini Index).

Three large prospective studies – the English Longitudinal Study on Ageing, the Irish Longitudinal study on Ageing and the Survey on Health, Ageing and Retirement in Europe – provided individual-level data on over 45,000 individuals aged 50-plus (average age approx. 65 years, approx. 57% female) from 18 European countries1, with a follow-up period of up to 11 years.  About 20% of the participants were from Ireland or the UK (more than 5,000 from Ireland and more than 3,850 were from the UK).

The individual-level factors included age, gender, BMI, smoking and physical activity, as well as whether the participant had been diagnosed with diabetes (type 1 or type 2) and their score on symptoms of depression (CES-D and EURO-D scale). (The 15% of participants with the highest scores were categorised as having high depressive symptoms.)

Austria was used as the ‘comparator’ country, as it was the first in alphabetical order in the countries studied – although the authors also note by coincidence the EASD meeting is taking place in Vienna, Austria this year. The study found that the odds of someone without diabetes or high depressive symptoms going to develop one of the conditions varied from country to country.

The odds of developing diabetes were lowest in the Netherlands and highest in Portugal. Compared with a person living in Austria, a person in the Netherlands had about 65% lower odds of developing diabetes, while someone living in Portugal had over 90% higher odds of doing so.

Meanwhile, the odds of developing high depressive symptoms were lowest in Denmark and highest in Italy. A person living in Denmark had about 20% lower odds of developing high depressive symptoms than one in Austria, while a person in Italy had odds nearly 150% higher.

(See tables in links to editor for other countries including UK and Ireland)

Despite this, the association between depression and diabetes was broadly similar for all of the country-level factors studied. People with high depressive symptoms had 15% higher odds of developing diabetes during the follow-up period than people with lower depressive symptoms, regardless of country’s quality of diabetes healthcare, expenditure, risk of poverty and gender and wealth inequality.

Conversely, people who were living with diabetes were at 48% higher odds of developing high depressive symptoms than people without diabetes.

All of the factors studied affected the risk of developing diabetes. They all also affected the risk of developing depression.

However, only one of the factors, BMI, influenced the association between diabetes and depression. The higher the BMI of a person with diabetes, the greater their likelihood of developing high depressive symptoms.

Specifically, each one-point increase in BMI in a person with diabetes increased their odds of developing high depressive symptoms by 2.1%.  This compares to a 1.3% increase per BMI point in a person without diabetes.

Unlike previous research this study did not find that the quality of diabetes care influenced the link between diabetes and depression.  This may be because of differences in the populations analysed.  For example, this study focused on people aged 50-plus and quality of diabetes care may have a greater impact on younger people.  

It could also reflect the different methods of research.  The previous study was cross-sectional, meaning it looked at just one point in time.  This study was longitudinal and so measured levels of diabetes and depression over time.

Together, the results suggest that the association between diabetes and depressive symptoms varies little between different countries and different sociodemographic groups.

Dr Gottfried concludes: “The way diabetes and high depressive symptoms are connected in people aged 50-plus is similar across European countries regardless of the quality of diabetes healthcare and other country-level factors like poverty rates or wealth inequality.

“As a result, the strategies that prevent someone with diabetes developing depression – or a person with depression developing diabetes – in one country should also be beneficial when implemented elsewhere.”re

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