Tea intake may cut abdominal aortic aneurysm risk

In two population-based Swedish cohorts of men and women with generally low tea consumption, tea intake was inversely associated with the incidence of abdominal aortic aneurysm (AAA).

The prospective study comprised 45,047 men from the Cohort of Swedish Men and 36,611 women from the Swedish Mammography Cohort. Tea consumption was evaluated by using food frequency questionnaires in 1997 and 2009. Mean frequency of tea intake was 1.3 cups/day in both cohorts of men and women who reported tea consumption.

During a mean follow-up of 17.5 years, a total of 1,781 incident AAA cases were identified (n=1,496 [men] and 285 [women]). A majority of the cases were non-ruptured AAAs (84 percent). Also, most of the ascertained AAA cases were found in men (84 percent) and in smokers (45 percent [current] and 36 percent [ex-smokers]). [BJS 2022;109:346-354]

After adjusting for a number* of risk factors, baseline tea consumption was inversely associated with risk of AAA (hazard ratio [HR], 0.90). When stratifying by sex, women had a 23-percent lower risk of AAA for tea consumption of at least one cup/day, whereas in men, the risk was 9 percent lower (p_interaction=0.029). The association was more pronounced for ruptured vs non-ruptured AAAs (HRs, 0.84 vs 0.93).

The researchers attributed this effect to the high flavonoid content of tea, as this could reduce systemic oxidative stress and inflammation which, in turn, trigger AAA development. [Arterioscler Thromb Vasc Biol 2002;22:560-565]

“[We also aimed to address] the question of whether oxidative stress-related AAA risk factors such as smoking status, hypertension, and hypercholesterolaemia modified the observed association,” said the researchers.

Smoking status did modify the association (p_interaction<0.001), particularly among ex-smokers (HR, 0.89) and never smokers (HR, 0.88), but not in current smokers (HR, 0.95). “It is possible that oxidative stress and systemic inflammation might be too high in current smokers to reduce AAA incidence by intake of tea flavonoids,” the researchers explained.

They also found a more pronounced association in individuals with hypertension and hypercholesterolaemia (HRs, 0.88 and 0.82, respectively) compared with those without (HRs, 0.93 and 0.92).

“Generally, tea is considered a beverage with the potential to reduce blood pressure, which may explain the stronger associations among participants with hypertension,” said the researchers. “Their essential role includes relaxing smooth muscle contraction, enhancing endothelial nitric oxide synthase activity and, as a result, improving endothelium-dependent vasorelaxation, reducing vascular inflammation, inhibiting renin activity, and reducing antivascular oxidative stress.”

Regarding hypercholesterolaemia, the validity of the data may have been influenced by statin use in patients even without high low-density lipoprotein levels, the researchers noted.

Also, data on the relationship between tea intake and lipid profile are conflicting, as some have observed benefits whereas others did not find any. [Damianus J Med 2021;20:40-45; PLoS One 2014;9:e107711; ClinNutr 2015;34:612-619] “[H]owever, it should be emphasized that high doses of tea or tea components are usually employed in animal studies, which may [have affected] the results,” they added.

Despite the encouraging results, the study is not without limitations. Several factors such as lack of analysis on different tea variants and misclassifications in self-reports should be taken into context. It was noted that individuals who consumed at least two cups of tea daily were less likely to have comorbidities, thus reflecting generally healthier behaviour amongst participants. “[H]ealthier physical status might lead to less interaction with healthcare services and therefore a lower rate of detection of aneurysms in unscreened cohorts,” said the researchers.

“Moreover, although the HRs were adjusted for many potential risk factors, a risk of potential residual confounding and its effect on attenuation of the observed associations cannot be excluded,” they added.