The study said talking on phone for 30 mins a week increased riskResearchers claim people who spend just 30 minutes talking on their mobile phone a week have a higher risk of stroke and heart attacks. A team of scientists said radio waves emitted by the endemic devices can cause high blood pressure in users over a prolonged period of time. High blood pressure is linked to an increased risk of stroke and heart attack and around one in four adults in the UK has the condition, The Sun reports. “Use of a hands-free set-up had no influence on the likelihood of developing high blood pressure. According to the Times no one taking part in the study had high blood pressure when it began.