Brisk activity tracked with 32% lower cardiovascular risk in 5,186 Dutch adults wearing thigh accelerometers

Most of what is known about exercise and the heart rests on what people say they do. Questionnaires underestimate sedentary time and rarely provide data on light activity, so researchers linking activity to heart disease have long been measuring memory and good intentions as well as movement.

A team at Maastricht University in the Netherlands used a sensor instead. They studied 5,186 adults, average age 59, who had worn a small motion sensor taped to the thigh for about a week, then followed them through annual questionnaires and government registration, meaning national health records, for a median of six years. Over that time there were 654 heart attacks, strokes and other blockages of the blood vessels. The most active quarter, who logged more than about 70 minutes a day of moderate-to-vigorous activity, had about a third lower risk than the least active quarter. Weekend warriors did about as well as people who spread their exercise through the week, and total time spent sitting showed no link to cardiovascular disease at all. Xiangyu Cui led the study, with Annemarie Koster as senior author, and it was published on October 6 in Medicine & Science in Sports & Exercise.

What a thigh-worn accelerometer measures

An accelerometer is a small motion sensor. The Maastricht Study, a long-running Dutch cohort that focuses on type 2 diabetes and its complications, uses one called the activPAL3. It weighs 15 grams, is waterproofed in a sleeve and is taped to the front of the right thigh, and participants wear it for eight consecutive days without removing it. Because it registers the angle of the thigh, the device also determines posture (sitting or lying, standing and stepping). A thigh lies flat when you sit and points down when you stand, so the sensor can tell sitting from standing still. A wrist or hip sensor has to infer the difference.

That has long been a weak spot in the field. The team behind the Women’s Health Study, one of the few large device studies, noted that few studies have investigated associations between device-measured activity and actual cardiovascular disease. A separate UK Biobank analysis led by Rema Ramakrishnan added that past work mostly relied on self-reported activity. Even device studies can blur the categories. With a hip-worn monitor it is easy for sitting to be misclassified as very light movement, as the Women’s Health Study team acknowledged about their own data. The Maastricht researchers could separate sitting, breaks from sitting, light activity and harder activity, and test each one against the same 654 cases of cardiovascular disease, or CVD, the umbrella term for heart attacks, strokes and blocked blood vessels.

The cohort recruited people aged 40 to 75 living in the southern part of the Netherlands and deliberately included extra participants with type 2 diabetes. About half of those in this analysis were women. Intensity is judged by the pace of stepping. In the cohort’s published methods, light intensity physical activity, defined as standing or stepping at under 100 steps a minute, sits at the bottom of the scale. Moderate-to-vigorous activity starts at 100 steps a minute and vigorous activity at 130.

Harder activity tracked with less cardiovascular disease

The clearest signal came from intensity. The top quarter for moderate-to-vigorous activity logged more than 69.8 minutes of it a day. Compared with the bottom quarter, they had about 32% lower CVD risk. Vigorous activity told the same story on a far smaller dose. The top quarter there needed only about 12 minutes a day of vigorous-intensity physical activity, and their risk was about 31% lower. Both comparisons pit the best-placed quarter against the worst-placed, so they say little directly about what one extra walk would do.

Some groups appeared to gain more. The link between moderate-to-vigorous activity and cardiovascular disease was stronger in women, and in limited-mobility individuals, meaning people who reported having difficulty walking 500 meters or climbing a flight of stairs. The second group stands out, since they are the participants for whom 70 minutes a day is hardest to reach. Both subgroup signals come from tests of whether the link differed between groups, and signals of that kind need repeating in another cohort before anyone leans on them.

Light activity was a different matter: standing and slow stepping did not line up with cardiovascular risk in either direction. The authors, who abbreviate physical activity as PA, end their summary on a hedge: “Overall, higher-intensity PA could be relevant for cardiovascular protection.” The “could” matters, because the study cannot say why intensity would count for more than volume. An earlier analysis of the same cohort offers one hint. People doing the most vigorous activity had lower levels of NT-proBNP, a blood marker of strain on the heart and one of the biomarkers of cardiac injury that are used clinically to diagnose heart failure. That analysis found no consistent pattern for troponins, the markers doctors use to confirm a heart attack.

Weekend warriors and daily exercisers had similar cardiovascular risk

The team also sorted people by the shape of their week. Anyone reaching 150 minutes of moderate-to-vigorous activity counted as active, and active people who did at least half of it on one or two days were labeled weekend warriors. Weekend warriors and regularly active individuals both had lower risk than people who were inactive or insufficiently active, by about 40% and 34%. The uncertainty ranges around those two figures overlap almost entirely, so the two patterns did about equally well and neither can be called the better one.

That matches the largest device study of the question. Shaan Khurshid and colleagues at Massachusetts General Hospital analyzed 89,573 UK Biobank participants who wore a wrist device for a week, and 42% of them fit the weekend-warrior pattern, more than were regularly active. People who packed their activity into one or two days had similarly lower risk of heart attack, heart failure, stroke and an irregular heartbeat called atrial fibrillation as those who spread it out.

Neither result sits awkwardly with current guidance. The World Health Organization’s 2020 guidelines ask adults for 150 to 300 minutes of moderate activity a week, 75 to 150 minutes of vigorous activity, or some equivalent combination of the two. They set no rule about which days the minutes fall on.

Sedentary time showed no link to cardiovascular disease in Maastricht

In the Maastricht data, total sitting time, long unbroken spells of sitting and the average length of a sitting spell were not associated with CVD. That runs against several earlier studies. The Women’s Health Study followed 16,031 US women aged 62 and older for about seven years. Those who spent less than 7.4 hours a day sedentary had a 33% lower hazard of total cardiovascular disease than those who sat for 9.5 hours or more. Ulf Ekelund at the Norwegian School of Sport Sciences led a pooled analysis of eight cohorts, which found that less time spent sedentary went with substantially reduced risk for premature mortality. That analysis counted deaths from any cause, so it speaks to sitting and survival more than to the heart.

The studies could differ without either being wrong. The Women’s Health Study used hip-worn devices, which can mistake sitting for very light movement, while the thigh sensor keeps the two apart. Its participants were also older, and all were women. And the Maastricht data did hold one sitting-related signal. Moderate numbers of breaks were associated with a lower risk than the fewest breaks: about 31% lower in the third quarter, at roughly 32 to 43 breaks a day, and about 25% lower in the second. The authors attach the benefit to moderate numbers of breaks, which suggests something other than a simple more-is-better line and makes it harder to read than the intensity signal.

The WHO guideline committee had already recognized the uncertainty. It recommends less sedentary time for everyone, but the evidence was insufficient to quantify how much sitting is too much, and the committee added that swapping sitting for activity of any intensity, light included, has health benefits.

Limits of one week of accelerometer data

This was an observational study. People who exercise hard differ from those who do not in many ways besides exercise, and statistical adjustment can only account for the differences that were measured. Reverse causation is a further worry. People whose cardiovascular disease is developing but not yet diagnosed may already be moving less, so low activity can be an early sign of illness as well as a possible cause. Ramakrishnan’s team said it could not completely dismiss the likelihood that this affected its own UK Biobank results.

Activity was captured over roughly a week, and that week stands in for six years of life. The cohort is Dutch, middle-aged to older and deliberately rich in people with type 2 diabetes, so the size of the differences may not carry over to younger or healthier groups. With 654 events divided among quarters of activity, the estimates are fairly wide, and the subgroup results and the weekend-versus-daily comparison are less certain than the main result for intensity.

Ramakrishnan’s study of activity and cardiovascular disease also shows how far such estimates can shift. Its first published estimates were later corrected after a coding error led to an underadjustment for age, and the corrected figures were weaker. Even so, the most active quarter, relative to the lowest fourth, still had about 42% to 44% lower cardiovascular risk. The authors’ conclusion that they found no evidence of a threshold, a point beyond which more activity stopped helping, still stands.

What the accelerometer results add to exercise guidelines

The Maastricht data agree with the part of the evidence that keeps replicating: brisker, harder activity went with fewer heart attacks and strokes, here in a cohort where activity was measured by a device and not recalled. Nothing in the study changes the WHO targets, which already let the minutes fall on any day of the week. How much activity suits a person with heart disease, limited mobility or diabetes is assessed by their doctor.

Sitting is the open question. A sensor built to tell sitting from standing found no link between total sitting time and cardiovascular disease, where other studies have found one. In six years of Maastricht data, effort was what tracked with a healthier heart.