A new study suggests that US adults with a family history of cancer may face a higher risk of developing long COVID, even if they have never had cancer themselves.

The analysis, led by researchers at Augusta University in Georgia and published in Cancer Causes & Control, used data from more than 25,000 adults who participated in the 2023 National Health Interview Survey. It found that those with a first-degree relative (parents, siblings, or children) with cancer were more likely to report post-COVID symptoms lasting at least three months. 

After adjusting for demographic and socioeconomic factors, the researchers estimated that adults with a family history of cancer were 26% more likely to experience long COVID than those without a close relative with cancer. 

Overall, approximately 8.4% of adults in the study reported having long COVID. Among those with a family history of cancer, the prevalence rose to nearly 9.6%, compared with roughly 7.6% of those without a family history. The association was most pronounced among adults aged 35 to 49 years, who had a 35% increase in the prevalence of long COVID. 

Underlying health conditions may play a role

When the researchers did a more granular analysis of the data, they found that about 30% of the link between a family history of cancer and long COVID may be explained by underlying health conditions such as obesity, asthma, anxiety, and depression. 

“This makes sense,” write the authors, “as adults with a family history of cancer had higher prevalence rates of certain health conditions, and the risk of Long COVID was higher among adults with underlying health conditions.” They note, as an example, that the rate of obesity was 3.5% higher among individuals with a family history of cancer, and the rate of long COVID was 3.4% higher among those who were obese.

But underlying health conditions don’t explain the entire association between family cancer history and long COVID. “A substantial direct effect was found for adults of age 35–49 years,” the authors note. 

A family history of cancer may reflect genetic susceptibility, immune dysregulation, or environmental exposures that influence vulnerability to post-viral illness. Previous research has identified cancer as a risk factor for long COVID, but the current study is among the first to examine a link between familial cancer history and long COVID.

Because the analysis relied on self-reported data, the authors caution that causal relationships cannot be established, and while they controlled for demographic, clinical, and behavioral factors, residual confounders such as genetic susceptibility, environmental exposures, or health-seeking behaviors may have influenced the findings.

Despite these limitations, the authors note, the findings provide new insight into factors associated with long-COVID risk. “By identifying the family history of cancer as an independent risk factor, our study expands the current understanding of Long COVID risk factors beyond personal medical history to include potential hereditary or shared biological influences,” they write.