I hate studies like this. The researchers controlled for age, sex, body mass index, race, deprivation, family history of hypertension, education, smoking status, blood pressure, blood lipids, inflammation, blood glucose, kidney function and use of medications to lower cholesterol or blood glucose levels. But there are a million other potential causal factors that could be correlated with talking on the phone. For instance, stressors in your life can be a reason to talk on the phone, and stress is linked with hypertension. I think these types of studies can be fine if it's clear that this is just a correlation, but the researchers seem to be presenting this as if they've established a causal relationship.

> Professor Qin said: “Our findings suggest that talking on a mobile may not affect the risk of developing high blood pressure as long as weekly call time is kept below half an hour. More research is required to replicate the results, but until then it seems prudent to keep mobile phone calls to a minimum to preserve heart health.”

I really wish more work was done to establish a causal relationship before publishing something like this.