Patients who have spring operations are more likely London - Arabstoday We all know you’re more likely to suffer colds in winter and hay fever in spring. But as ROGER DOBSON reveals, there are many, far more unexpected ways in which different times of the year can affect your health... JANUARY Increased cholesterol levels, gum disease and death rates Levels of bad cholesterol and triglycerides (fats in the blood linked to heart disease) peak in January and December, according to a Harvard University report, and are lowest in the summer.   In fact, another study found the difference is so great that up to 22 per cent of people diagnosed with high cholesterol in winter would not have the same diagnosis in summer. The reason for this is not clear. One theory is that either the higher temperature or raised levels of physical activity in summer increases the amount of fluid in the bloodstream in which blood cells are suspended — called plasma — which may dilute cholesterol levels. This month is also peak time for deaths from all causes. On average, around 250 more people die in the UK each day this month compared to August. Most of these ‘excess’ deaths are linked to lowered resistance to illnesses because of a less active immune system. Research has shown that T cells, crucial bug-fighting components of the immune system, are at lower levels during the winter. Scientists have also found that gum disease peaks in winter, which may also be linked to a lower immune system. FEBRUARY Greater risk of retinal detachment The month sees a rise in the risk of detached retina, where the light-sensitive layer at the back of the eye pulls away from the blood vessels that supply it. This is serious and can lead to blindness if not treated quickly. A study at Princess Margaret Hospital, Swindon, found twice as many cases at the beginning of the year, with a 40 per cent increase in risk; it’s thought cold weather may make eye tissue more vulnerable. Sperm count is highest in February and March and the lowest during September, according to research in Fertility and Sterility journal — it’s not clear why. MARCH Peak time for cold sores March and April see the most cold sores, with another spike in August, according to a study in the Journal of Interdisciplinary Cycle Research. Low immune defences may be responsible for sores in spring, while sun exposure, which can also reduce the immune system’s strength, may be responsible in August. But March may be one of the safest time for surgery. Patients who have spring operations are more likely to survive, according to research based on nearly 200,000 lung cancer patients. Those treated in the winter had a 33 per cent increased risk of dying. Similar increases have been found for other procedures, including heart bypass. U.S. researchers link this to seasonal variations in factors such as depression and lifestyle. APRIL Increased rate of  ‘cluster’ headaches Spring is peak time for cluster headaches, with another high around September. ‘We do notice seasonality affects the numbers of patients referred to headache clinics, particularly cluster headache — probably the most severe pain known to man,’ says Dr Nicholas Silver, a neurologist at Liverpool’s Walton Centre. It is linked with the hypothalamus, the brain area which controls the body clock and hormonal fluctuation. MAY Worsening of inflammatory bowel disease and increased rate of multiple sclerosis relapses Symptoms of IBS (such as diarrhoea and constipation) are more frequent in spring and summer. In patients with Crohn’s disease they were 59  per cent more frequent than in autumn and winter, and higher by 27 per cent in those with ulcerative colitis. The research, in Digestive And Liver Disease journal, says infections and seasonal changes in immune functioning may be involved. Relapses for multiple sclerosis are three times more frequent in May than September, according to a study at the University of Ferrara, Italy, possibly because of seasonal changes in the immune system. JUNE Lower blood pressure Seasonal variations aren’t all bad news — at this time of year blood pressure is at a yearly low. Doctors who carried out the French Three-City study, which monitored 8,801 elderly people, found blood pressure was higher in winter. Professor Frank Ruschitzka, from University Hospital Zurich, says one possible explanation is that vitamin D, which is more plentiful in summer, may activate hormones that regulate blood pressure. JULY Leg ulcer rates increase and appendicitis cases rise Leg ulcers are more frequent during the summer, and those treated in summer healed slower. ‘Seasonal variations in immune system activity might be responsible,’ write researchers in the journal Phlebology. Risk of acute appendicitis is highest this month, according to study of 1,300 cases by doctors in Ferrara, Italy. AUGUST Higher PSA levels and better cancer outcomes Levels of prostate-specific antigen (PSA) — linked to prostate disease — are higher in the summer, according to a report in European Urology journal. Researchers suggest that this may be linked to vitamin D. A study of more than one million cancer patients in the UK shows those diagnosed in summer and autumn are likely to survive longer. Sunlight is essential for the production of vitamin D, and evidence suggests the vitamin may have a role in stopping tumour growth. SEPTEMBER Asthma symptoms worsen Hospital admissions of children with asthma peak in the first four weeks of school after the summer holidays, according to research reported in Public Health — the obvious link is between a return to school and infections. OCTOBER Worsening of stomach ulcers, arthritis and acne This month is the peak time for hospitalisation for peptic ulcers (while August has the lowest rate). A study at the Russian Academy of Medical Science on duodenal ulcers suggests that melatonin, the sleep hormone triggered by daylight, may be involved as the days get shorter. Onset of rheumatoid arthritis, an auto-immune disease, is twice as frequent between October and March as other times. Symptoms also tend to be worse during winter, possibly because of changes in immune system activity.   Acne consultations begin to peak, after a summer low. Sun exposure and vitamin D may ease symptoms in summer. NOVEMBER Worsening of lung disease and psoriasis symptoms, baby blues peak Symptoms of chronic obstructive pulmonary disease (COPD) are twice as bad during winter, according to Woolcock Institute in Sydney. Women who give birth in the last three months of the year are twice as likely to develop post-birth depression, according to a Swedish study. This is also the peak time for psoriasis consultations. An Indian study shows that 42  per cent worsened in winter. Differences in ultraviolet light may be partly responsible. DECEMBER Peak time for coughs, premature births rise People are more likely to suffer from coughs now, according NHS Direct data. Annual peaks in calls occurred in late December. Rates of pre-eclampsia — dangerously high blood pressure in pregnancy — are higher for winter delivery, according to University of Iowa study. ‘Seasonal variation in infectious diseases, asthma, vitamin D levels, and nutrition may all play a role,’ say researchers.