Long-Lived Parents, In-Laws Linked to Lower Risk for Type 2
People with parents who live into their 90s are less likely to develop type 2 diabetes — and so are their spouses, according to a new study published in the journal Frontiers in Clinical Diabetes and Healthcare that may pose more questions than it answers about the relationship between family health history and diabetes risk.
It has long been known that a family history of type 2 diabetes is one factor that makes a person more likely to develop the condition. A family history of diabetes may also increase your risk for prediabetes, or elevated blood glucose that doesn’t reach the threshold for a diabetes diagnosis. But a family history of type 2 diabetes isn’t just related to your diabetes risk — one recent study found that it’s also linked to your risk for nonalcoholic fatty liver disease (NAFLD), even if you don’t develop diabetes. And it stands to reason that a family history of other health conditions — or certain outcomes like longevity — might also be linked to your risk for type 2 diabetes.
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For the latest study, researchers were interested in looking at how having parents with “exceptional longevity” — living to be at least 90 years old — might affect the risk for type 2 diabetes, a topic that hadn’t been explored in previous research. They used data from a family-based study called the Long-Life Family Study, which recruited participants at centers located in Boston, New York City, and Pittsburgh in the United States, as well as in Denmark. A total of 583 families enrolled in the study, with researchers gathering information on people who lived to be at least 90 while enrolled in the study, as well as on their siblings, their offspring, and their offspring’s spouses.
Among the second generation of participants in the study — offspring and their spouses — the average age was 60, with an age range from 32 to 88. For the purposes of the study, having type 2 diabetes was defined as a fasting blood glucose level of 126 mg/dl or higher, an A1C level (a measure of long-term blood glucose control) of 6.5% or higher, a self-reported diagnosis by a doctor of type 2 diabetes, or taking a glucose-lowering medication. Both previously existing and new cases of type 2 diabetes were recorded over an average follow-up period of 7.9 years.
Lower-than-average rates of type 2 diabetes found
Out of 1,105 offspring and 328 spouses ages 45 to 64 who didn’t have type 2 diabetes at the beginning of the study, the annual rate of new cases of diabetes was 3.6 per 1,000 person-years for offspring and 3.0 per 1,000 person-years for their spouses. Out of 444 offspring and 153 spouses ages 65 and older who didn’t have type 2 diabetes at the beginning of the study, the annual rate of new cases of diabetes was 7.2 per 1,000 person-years for offspring and 7.4 per 1,000 person-years for their spouses. In comparison, the annual rate of new cases of type 2 diabetes in 2018 in the United States was 9.9 per 1,000 person-years for people ages 45 to 64, and 8.8 per 1,000 person-years for people ages 65 and older.
The researchers noted that it’s fairly clear why there might be a link between longevity in parents and a low risk for type 2 diabetes in their offspring — these offspring could have inherited a low genetic risk for serious health conditions, including diabetes. But it’s less clear why the spouses of these offspring also appear to have a low risk for type 2 diabetes. On potential explanation is shared lifestyles, according to an article on the study at Medscape — spouses often share similar healthy or unhealthy habits, such as shared leisure activities or alcohol consumption habits. In fact, data from the study suggests that spouses of offspring tended to have healthier lifestyle than the offspring themselves. Another potential explanation is “assertive mating,” meaning that people tend to choose spouses — consciously or unconsciously — with a similar level of personal or family health.
“Our findings […] raise the possibility that distinct biological risk and protective factors may contribute to [type 2 diabetes] risk among offspring of long-lived individuals when compared with their spouses,” the researchers wrote. “Future studies are needed to identify the mechanisms underlying low [diabetes] risk among the offspring of individuals with exceptional longevity, and also among their spouses.”