Why do the disadvantaged suffer more Type 2 diabetes?

WASHINGTON — The twin plagues of economic hardship and low academic attainment turn out to be an inflammatory problem, not just for society but for the human bodies beset by them. And for many, including those in minority groups who disproportionately experience stunted economic and academic prospects, high rates of Type 2 diabetes are the common result, a new study says.

The new research, based on a long-running study of British government workers, offers a partial explanation for a trend that is firmly established in industrialized democracies — that where calories are plentifully available, those clinging to the lower rungs of the economic ladder are most likely to develop Type 2 diabetes. The study was published Tuesday in the open-access journal Public Library of Science (PLoS) Medicine.

The “Whitehall II” study tracked 6,387 London-based civil servants, who were between 35 and 55 years old when they were recruited, for as long as 24 years starting in 1985. In the study phase that began between 1991-93, none had diabetes. Roughly every two years thereafter, researchers weighed subjects, administered glucose tolerance tests, inquired about diabetes diagnoses and health behaviors, and drew blood samples to test levels of the inflammatory markers Interleuken-6 and C-reactive protein.

The researchers also set out to characterize participants’ socioeconomic “life course.” They gauged participants’ socioeconomic status in childhood from their accounts of the work their fathers did. A few years into the study, researchers classified each participant’s employment grade — from clerical/support up to the most senior civil servants. And 10 years into the study, they asked about a participant’s highest level of educational attainment. The resulting answers established where subjects fell on the socioeconomic ladder, and whether their status had risen or fallen over the course of their lives.

True to past research, those on the lower rungs of the societal ladder were more likely to develop Type 2 diabetes during the study period than those with more education and rosier economic circumstances. They also had poorer health behaviors that would help explain their higher diabetes rates: Compared to those in higher positions with more education, they were more likely to smoke, to be sedentary, to be obese, and to have an unhealthy diet.

But irrespective of such behaviors, the participants with lower lifetime socioeconomic status also showed higher levels of inflammation in their blood. And even after researchers adjusted for the effects of smoking, lack of exercise and bad diets (all of which would push inflammatory levels up), higher levels of inflammation among those on society’s lower rungs explained close to a third of the diabetes cases that developed over the years.

Upward social mobility (yes, even in London) certainly helped: Among those who had grown up in constrained economic circumstances but attained high educational levels and bettered their fathers’ occupational standing, inflammation levels came down, and diabetes rates fell below that of peers who’d been advantaged since birth. Downward social mobility left participants a little healthier than those who’d spent a lifetime low on the ladder, but not much.

“Our results suggest that tackling socioeconomic differences in inflammation, especially among the most disadvantaged groups, might reduce social inequalities in Type 2 diabetes,” the authors wrote. Those might include weight management, physical activity and smoking cessation programs, and possibly anti-inflammatory drugs.

Notably not suggested were reforms that could improve the educational prospects of children from low-income families, worker benefits that could give clerical and support workers more flexibility and control over their work lives, and tax policies that fostered social mobility.