In women, higher triglycerides came before stiffer arteries three years later. Then 2,989 UK adults' blood pressure was put into the model, and the link no longer held up

Stiff arteries and poor blood fats both raise the risk of heart disease, and they tend to turn up in the same people. What is less clear is which one leads. A team from Peking University Shenzhen Hospital and BGI Genomics in Shenzhen tried to sort out the order using the UK Biobank, the long-running study of half a million British adults. They picked out 2,989 people, 1,544 men and 1,445 women in their late fifties on average, who had both blood fats and a pulse-wave reading taken at their first visit and again about three years later (median 3.0 years). The paper appeared in Frontiers in Nutrition on 29 October.

Arterial stiffness here was not measured the way cardiologists usually prefer. Instead of timing a pulse between the neck and the groin, the UK Biobank used a sensor that records the shape of each pulse wave, and from it worked out an arterial stiffness index, a reflection index and the gap between the wave's two peaks. The team then ran cross-lagged models, which ask whether a person's level of one thing at the first visit predicts where they sit on the other at the second, in both directions at once, and corrected for the many pairs tested (seven blood-fat measures against four pulse measures, in each sex).

In women, the pattern ran one way. Higher triglycerides at the start went with a higher stiffness index three years on (standardised estimate 0.071, corrected p = 0.013) and a shorter gap between the pulse peaks, which also points to stiffer vessels. In a second model that adjusted for 15 more blood measures, from liver enzymes to vitamin D and sex hormones, higher triglycerides went with a higher reflection index and a slightly lower pulse rate later. Going the other way, stiffness at the start did not predict blood fats later in either sex. In men the only signal was apolipoprotein B, the protein on LDL and other cholesterol-carrying particles, and it went the opposite way to what you might expect: higher ApoB came before a slightly lower reflection index (estimate -0.057, corrected p = 0.049).

Then came the test that matters most. Blood pressure stiffens arteries and changes alongside blood fats, so the team let systolic blood pressure change over time in the model too. With that in, the links from blood fats to stiffness were no longer statistically significant. Only the tie between triglycerides and later pulse rate in women survived, plus one link running the other way, from pulse rate to later cholesterol. The authors read this as a sign that the associations may run through, or be tangled up with, blood pressure, and they list their own limits plainly: a modest sample for this kind of model, only two time points, no gold-standard pulse wave velocity, and volunteers who came back for a repeat visit, all middle-aged or older and living in the UK. It is a hint about order, not proof that triglycerides stiffen arteries, and it says nothing about whether lowering them would help.