Exposure to higher concentrations of air pollutants such as particulate matter of various sizes and nitrogen oxides is also associated with a higher risk of cardiovascular disease, which is a common secondary disease of diabetes with high clinical relevance. But the importance of air pollution for other complications of diabetes, especially peripheral neuropathy, is still unclear. The most common form of peripheral neuropathy is distal sensorimotor polyneuropathy (DSPN), which is one of the most common comorbidities in people with diabetes, but according to recent studies is also becoming more common in people with severe obesity. Symptoms range from mild sensory disturbances to pronounced pain primarily in the feet and lower legs. Treatment options are only symptomatic and not cause-specific, which complicates the treatment of individuals with DSPN.

A study conducted by the German Diabetes Center (DDZ) and Helmholtz Zentrum München has now investigated the association between air pollutants and the incidence and risk of DSPN in a population-based study of elderly people with high rates of type 2 diabetes and obesity. The cross-sectional analyses were based on 1,075 individuals aged 62 to 81 years from the KORA F4 study (KORA: Cooperative Health Research in the Region of Augsburg). The analyses of new cases of DSPN used data from 424 people who did not have DSPN at baseline and of whom 188 had developed the disease in the 6.5 years up to the data collection. The exposure to air pollutants was recorded on the basis of the annual average concentrations at the place of residence.

The results show that although there is no higher risk of neuropathy with higher air pollution levels in the entire study population or in people with diabetes, they are found in people with obesity. Obesity and air pollution can thus have synergistic effects on the development of DSPN. "These study data suggest that not all individuals respond in the same way to air pollutants, but that there are certain groups in the population for whom air pollutants are associated with particularly high health risks," said Professor Christian Herder of the DDZ. Since the causes that lead to polyneuropathy are so far insufficiently known, these results identify a new potentially modifiable risk factor.

"The next step will be to confirm this association in additional cohorts," said Professor Dan Ziegler, deputy director of the Institute for Clinical Diabetology at the DDZ. "From a clinical perspective, the identification of air pollution as a potential new risk factor of DSPN raises the question of the extent to which environmental factors may contribute to this disease," said Prof. Michael Roden, scientific director and member of the board of the DDZ, commenting on the findings. "These data thus underscore the importance of interventions to reduce exposure to air pollution and strategies to prevent obesity in the general population."