A study published in the journal BMC Public Health finds that poor adherence to the Mediterranean diet and the presence of sleep disorders increase the risk of all-cause mortality and cardiovascular disease-related mortality in the US population.

Study: Sleep disorder, Mediterranean diet, and all-cause and cause-specific mortality: a prospective cohort study. Image Credit: PrinceOfLove / Shutterstock

Background

Consumption of a poor-quality diet is associated with chronic, low-grade inflammation, oxidative stress, and nutrient deficiency. These factors collectively increase the risk of chronic diseases and mortality.

The Mediterranean diet contains high amounts of vegetables, fruits, whole grains, nuts, legumes, fish, unsaturated fatty acids, vitamins, and minerals, which are beneficial dietary components with positive health effects. This particular diet is known to improve cardiovascular health and reduce the risk of cardiovascular and metabolic diseases and certain types of cancers.

While the Mediterranean diet has been found to reduce the risk of all-cause mortality, cardiovascular disease-related mortality, and cancer mortality, studies investigating sleep disorders have shown that both longer and shorter sleep duration increases the risk of all-cause mortality and disease-specific mortality.

Dietary patterns and sleep disorders exhibit a bidirectional relationship. While food items containing melatonin are known to improve sleep quality, foods rich in added sugar, saturated fats, and caffeine are known to affect both the quality and duration of sleep.

In the current study, scientists have investigated whether adherence to the Mediterranean diet and the presence of sleep disorders have any synergistic effects on all-cause and disease-specific mortality in the US population.       

Study design

The study was conducted on 23,212 individuals from the National Health and Nutrition Examination Survey (NHANES), a national, cross-sectional survey conducted between 2005 and 2014 to assess the health and nutritional status of the US population.

Two days of 24-hour dietary recall data from the survey was used to determine the average dietary intake of the participants. A 9-point evaluation score, the alternative Mediterranean diet index, was used to determine adherence to the Mediterranean diet. The index is based on estimating the intake of different food components, including vegetables, fruits, legumes, nuts, whole grains, fish, red meat, monosaturated/saturated fat ratio, and alcohol.

Based on the alternative Mediterranean diet score, the participants were categorized into three groups, i.e., below median, median, and above median groups. Structured questionnaires were used to determine sleep disorder and sleep duration.  

The mortality assessment was conducted based on the National Death Index, which included all-cause mortality, cardiovascular disease-related mortality, and cancer-related mortality. The average follow-up time for the patients was 111.6 days.

Important observations

The relationship analysis between the alternative Mediterranean diet, sleep disorders, and mortality revealed that a lower alternative Mediterranean diet and the presence of sleep disorders significantly increase the risk of all-cause and cardiovascular disease-related mortality. However, no significant association between diet and sleep disorders was observed with cancer-related mortality.

A low alternative Mediterranean diet combined with a sleep disorder was associated with a lower long-term mortality rate. The highest risk of all-cause and cardiovascular mortality was observed among participants with both sleep disorders and a lower alternative Mediterranean diet.

A significant combined effect of the alternative Mediterranean diet and sleep disorder was observed on cardiovascular mortality. However, no such effect was observed on all-cause and cancer mortality.

A comparatively higher risk of all-cause and cardiovascular mortality was observed among participants with low to medium levels of alternative Mediterranean diet together with sleep disorders. However, no such effect was observed on cancer mortality.

Regarding different food components of the Mediterranean diet, the study found a significant interaction between whole grain intake and sleep disorder for all-cause mortality. Similarly, an interaction was observed between fruit, whole grain, legume consumption, and sleep disorder for cardiovascular mortality.

An interaction was also observed between alcohol consumption and sleep disorder for cardiovascular mortality. Among participants with sleep disorders, moderate alcohol consumption was not found to reduce the risk of cardiovascular mortality.

Study significance

The study reveals that poor adherence to the Mediterranean diet and the presence of sleep disorders collectively increase the risk of all-cause and cardiovascular mortality in the US population. However, no such effect has been observed for cancer mortality.  

Written by

Dr. Sanchari Sinha Dutta

Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the power of science in every corner of the world. She has a Bachelor of Science (B.Sc.) degree and a Master's of Science (M.Sc.) in biology and human physiology. Following her Master's degree, Sanchari went on to study a Ph.D. in human physiology. She has authored more than 10 original research articles, all of which have been published in world renowned international journals.