Seasonal variations affect the occurrence of risk factors for heart disease, as heart attack rates peak during the winter months and simmer down during the summer months, according to a recent study. The researcher's findings reveal that blood pressure, total cholesterol, and waist circumference are highest during the winter months, increasing the likelihood of heart disease. Dr. Pedro Marques-Vidal and a team of researchers from Switzerland used cross-sectional data from 10 population-based studies in the following seven countries: 21,128 subjects in Belgium, 15,664 in Denmark, 1,626 in France, 18,370 in Italy, 25,532 in Norway, 9,359 in Russia, and 15,411 in Switzerland. In total, the researchers obtained information on cardiovascular risk factors in 107,090 subjects between the ages of 35 and 80.

The participants’ blood pressure, lipids, glucose levels, body mass index (BMI), and waist circumference were measured to evaluate whether or not there was a pattern that could explain seasonality in heart disease deaths. The measurements were compared, according to the winter and summer season, and were adjusted for age, gender, and whether or not a participant smoked, reports Science Daily.

The researchers’ analysis showed that systolic blood pressure (BP) levels were on average 3.5 mmHg lower in summer than in winter. In general, natural low blood pressure levels mean lower risks of stroke or heart disease. However, if a sudden BP drop causes a person to feel faint or dizzy, then this is a cause for concern, says Blood Pressure UK.

In addition to lower BP levels, on average, the participants had a waist circumference 1 centimeter smaller in the summer, while their total cholesterol on average was 0.24 mmol/L lower during the hot summer months.

"Although this difference is almost irrelevant for an individual, it is considerable for a whole population because the whole blood pressure distribution is shifted to higher values, increasing cardiovascular risk," said Marquez–Vidal at the study's ESC Congress presentation. He believes the impact that seasons have on BP levels could have a significant impact on cardiovascular risk as genetic markers for blood pressure. “The joint effect of genetic markers on blood pressure is modest, between 2 and 3 mmHg."

A surprising finding for the researchers was that seasonal variation had an impact on waist circumference, but not on BMI in the participants during the year. Glucose levels were also found to remain the same. The researchers admit to not having a clear explanation for these results, but the start of a new study on seasonal food intake could help to better explain their results.

Overall, the findings support the belief that heart disease risk factors are more present during the winter holidays rather than over the summer. "People need to make an extra effort to exercise and eat healthily in the winter to protect their health,” Marquez-Vidal said. In the United States, heart disease causes an average of 193.6 deaths per every 100,000 people, according to the Centers for Disease Control and Prevention. Heart disease remains the leading cause of death for Americans.