Heated tobacco linked to hypertension, but causation remains unclear

Researchers in Japan followed more than 30,000 adults over roughly three years and found something that looked straightforward at first: people currently using heated tobacco products—devices that warm rather than burn processed tobacco—developed high blood pressure at higher rates than those who had never smoked. The gap was real enough in the primary analysis. Eight percent of heated tobacco users developed hypertension, compared to five percent of never-smokers. Current cigarette smokers and former smokers showed similar or slightly higher rates. The finding seemed to add weight to a growing concern: that these products, often marketed as safer alternatives to conventional cigarettes, might carry cardiovascular risks their manufacturers downplay.

But the story fractured when researchers dug deeper. When they ran the same analysis with different methodological adjustments—what scientists call sensitivity analyses—the association between heated tobacco use and hypertension weakened considerably. In some versions of the analysis, the link disappeared entirely and was no longer statistically significant. The researchers, based at Kindai University Faculty of Medicine, had to acknowledge what their own data was telling them: the connection they observed in the primary analysis was less robust than it first appeared.

The core problem is one that haunts observational studies: they can show that two things happen together, but they cannot prove one caused the other. Among the 30,979 Japanese adults enrolled between 2021 and 2025, many of the current heated tobacco users had previously smoked conventional cigarettes. The study recorded smoking status only at the beginning, not whether people changed their habits during the follow-up period. This means researchers could not separate the lingering effects of years of conventional smoking from any fresh damage caused by switching to heated products. A person who smoked for twenty years and then switched to heated tobacco might develop hypertension because of the old damage, the new product, or both—and the study cannot tell which.

Other confounding factors muddied the picture further. Tobacco users across all categories—whether they smoked conventional cigarettes, heated products, or both—tended to share certain lifestyle patterns. They were more likely to skip breakfast, eat late in the evening, eat quickly, gain substantial weight since early adulthood, and drink alcohol regularly. These behaviors cluster together and independently raise cardiovascular risk. When researchers tried to account for these differences statistically, the heated tobacco association weakened again. The study also could not track how often people used these products, how intensely, or for how long, nor could it capture the timing of any switches from conventional to heated tobacco.

The biological plausibility is there. Laboratory studies have shown that heated tobacco exposure triggers oxidative stress, endothelial dysfunction, and inflammatory responses in blood vessels—the same pathways through which conventional smoking damages the cardiovascular system. Human studies have documented acute increases in blood pressure and arterial stiffness after heated tobacco use. One experimental study found that blood pressure and pulse wave velocity increases after heated tobacco use matched those seen after conventional cigarette smoking, suggesting these products may not be the safer option their marketing implies.

Yet the observational evidence remains tangled. The study found that former smokers also had elevated hypertension risk compared to never-smokers, which makes sense given that smoking causes lasting vascular damage. But it also illustrates the challenge: if people who quit smoking years ago still carry excess risk, how can researchers isolate the effect of a product someone switched to recently? The Japanese cohort was also relatively young, averaging 46.8 years old, which limits how much these findings tell us about older populations or different demographic groups.

The researchers are careful in their framing. They found an association, not proof of causation. The study extends earlier findings from a smaller cohort of Japanese workers, suggesting the pattern may be real. But they also acknowledge what remains unknown: whether heated tobacco carries lower, higher, or equivalent cardiovascular risk compared to conventional cigarettes; whether the observed excess risk comes from the heated tobacco itself or from unmeasured prior smoking exposure; and whether these findings hold in other Asian populations with different smoking patterns and demographics. As heated tobacco use continues to rise across Asia, future studies with detailed histories of tobacco exposure and longer follow-up periods will be needed to answer these questions. For now, the evidence suggests caution, but it does not yet prove harm.