Trips to the toilet at night are a sign of high blood pressure, according to results from the Watari study presented today at the Annual Scientific Meeting of the Japanese Circulation Society.

Previous research from Japan has reported that high salt intake is associated with nocturia. Compared to western countries, people in Japan eat more salt and are more likely to be “salt sensitive”, meaning that their blood pressure rises more when salt is consumed. Taken together, these two factors mean that people in Japan are at greater risk of developing high blood pressure.

This study examined the link between nocturia and hypertension in the general Japanese population. The study enrolled 3,749 residents of Watari who had an annual health check in 2017. Blood pressure was measured and information on nocturia was obtained by questionnaire. Participants with blood pressure 140/90 mmHg or higher or prescribed antihypertensive drugs were considered hypertensive.

Nocturia (one or more nocturia events per night) was significantly associated with hypertension after controlling for possible confounders (odds ratio 1.4; p<0.01). The risk of hypertension rose significantly as the number of nocturia events per night increased (p for trend <0.01).

“We found that getting up in the night to urinate was linked to a 40% greater chance of having hypertension,” said Dr Satoshi Konno, of the Division of Hypertension, Tohoku Rosai Hospital, Sendai, Japan. “And the more visits to the toilet, the greater the risk of hypertension.”

Of the 1,882 participants who answered the questionnaire, 1,295 (69%) had nocturia. Dr Konno said the results do not prove a causal relationship between nocturia and hypertension and may not apply to populations outside Japan. He said: “The relationship may be influenced by various factors including lifestyle, salt intake, ethnicity, and genetic background.”

European Society of Cardiology President Professor Barbara Casadei said: “More than one billion people have high blood pressure worldwide. High blood pressure is the leading global cause of premature death, accounting for almost ten million deaths in 2015. ESC guidelines recommend medication to reduce the risk of stroke and heart disease. A healthy lifestyle is also advised, including salt restriction, alcohol moderation, healthy eating, regular exercise, weight control, and smoking cessation.”