With the onset of winter, the King George's Medical University (KGMU) and Ram Manohar Lohia Institute of Medical Sciences (RMLIMS) have recorded a 50 per cent rise in cases of stroke since November while a hospital in Lucknow, which rarely receives stroke patients, is also reporting cases.

According to officials, KGMU has been reporting an average of six cases of stroke daily since November which has now increased to around 10 to 12.

The number has gone up to 5 to 6 at RMLIMS. The hospital in Lucknow is recording at least one case on a weekly basis. An increase of 20 per cent has also been registered in the number of heart patients.

According to experts, a dip in temperature has triggered respiratory infections and constriction of blood vessels leading to a rise in blood pressure which is making people prone to brain haemorrhage, ischemic (clot) stroke or heart attack, and artery blockage.

Doctors said that people suffering from heart disease and hypertension should visit the doctor and get the dosage of their medicines revised.

Prof Ravi Uniyal, a faculty member at KGMU's neurology department, said, "If someone is already suffering from high blood pressure and is over 40 years of age, especially those with headache, must visit a doctor in winter. They should get their blood pressure checked and take medicines to control it."

Prof Pravesh Verma, a faculty at the cardiology department, said "Patients with respiratory infection have six times more possible to suffer a heart attack than a normal person. Low temperature causes blood vessels to constrict, so the heart has to pump harder to push blood through our constricted veins and arteries to organs. This makes those patients vulnerable who have a clot or plaque or have undergone heart surgery."

Prof Bhuvan Tiwari, head of the cardiology department, said, "Those above 40-45 years should avoid a sudden dip in body temperatures. They must wear layered clothing and socks to prevent sudden contraction of blood vessels which might cause a heart attack or stroke."

At least 50 per cent of patients, who suffer from heart attack and stroke cases do not know they are hypertensive. High blood pressure is the leading cause of heart attacks and strokes.

"People, especially those over 40, must get their BP checked from time to time. If it is deranged twice in the gap of a few hours, start taking medication," the doctors said.

"Since hypertension does not cause any symptoms, people tend to often quit medication thinking that they are fine," the doctors said.