Medical Bulletin 28/ March/ 2024

Is longer duration of exclusive breastfeeding associated with decreased risk of childhood cancers?

According to a study published in the journal JAMA Network Open, exclusive breastfeeding for at least 3 months has been associated with decreased risk of childhood hematologic cancers, particularly B-cell precursor acute lymphoblastic leukaemia, but not with risk of central nervous system or solid tumours.

Despite its rarity compared to adult cancers, childhood cancer remains a significant concern, with various types affecting young individuals. Leukaemia, brain tumours, lymphomas, and neuroblastomas are among the most prevalent forms. According to global statistics, approximately 300,000 children below the age of 15 are diagnosed with cancer each year.

Previous research has suggested that breastfeeding is associated with a reduced risk of childhood cancers, such as acute lymphoblastic leukemia (ALL), the most common cancer in childhood. Meta-analyses and pooled studies have shown that children breastfed for at least 6 months had an approximately 20% lower risk of developing ALL or leukaemia in general compared with those breastfed for shorter durations or not at all.

In the study, researchers used administrative data on exclusive breastfeeding duration from the Danish National Child Health Register. All children born in Denmark between January 2005 and December 2018 with available information on duration of exclusive breastfeeding were included. Children were followed up from age 1 year until childhood cancer diagnosis, loss to follow-up or emigration, death, age 15 years, or December 31, 2020. Data were analyzed from March to October 2023.

The result revealed that among the 3,09,473 children included in the study,332 children (0.1%) were diagnosed with cancer at ages 1 to 14 years. Of these, 124 (37.3%) were diagnosed with hematologic cancers (81 [65.3%] were acute lymphoblastic leukemia, 74 [91.4%] of which were B-cell precursor. Compared with exclusive breastfeeding duration of less than 3 months, exclusive breastfeeding for 3 months or longer was associated with a decreased risk of hematologic cancers, which was largely attributable to decreased risk of BCP-ALL, but not with the risk of central nervous system tumours or solid tumours.

The findings suggested that the association between breastfeeding and childhood BCP-ALL risk, if determined to be causal, could be mediated by preventing this immunologic dysregulation. Specifically, breastfeeding provides passive protection against infections and inflammation through antibody transmission and anti-inflammatory properties and also directly influences the shaping of the infant’s gut microbiome, important for immune system maturation.

Reference: Signe Holst Søegaard, PhD; Mie Mølgaard Andersen, BSc; Klaus Rostgaard, MSc; et al; Exclusive Breastfeeding Duration and Risk of Childhood Cancers; Journal: JAMA Network Open; doi:10.1001/jamanetworkopen.2024.3115

How is sodium intake associated with mortality outcomes?

According to a study published in the journal JAMA Network Open, exceeding the intake of sodium beyond the recommended daily amount is associated with 10% to 30% of Cardiovascular disease mortality.

Sodium is an essential nutrient for normal physiologic function, but excessive intake is associated with adverse health outcomes. For health promotion and disease prevention, the 2020 to 2025 Dietary Guidelines recommend less than 2300 mg of sodium per day.

Excessive sodium consumption has been linked to elevated blood pressure, a major risk factor for cardiovascular disease (CVD), and can directly affect multiple target organs and tissues, including the brain, heart, kidneys, and bones, contributing to increased mortality hazards. A report from the National Health and Nutrition Examination Survey (NHANES) found 46% higher CVD mortality among people with high-sodium diets.

In the cohort study, participants aged 40 to 79 years from the Southern Community Cohort were recruited from 2002 to 2009. Analyses were conducted between March 2022 and June 2023. Dietary sodium intake was assessed using a validated food frequency questionnaire at baseline. Multivariable-adjusted regression was used to estimate hazard ratios for mortality outcomes, i.e., all-cause, cardiovascular disease [CVD], coronary heart disease [CHD], stroke, heart failure, cancer, and others, associated with sodium intake.

The results revealed that compared with the recommended level of less than 2300 mg/d, higher sodium intake was associated with increased mortality. A 1000-mg increase in daily sodium intake was associated with a 3% higher risk of death from all-cause, a 7% higher risk from total cardiovascular disease, 8% higher risk from coronary heart disease. No significant dose-response associations were observed for any other mortality outcomes.

The findings suggested that high sodium intake can promote oxidative stress, endothelial dysfunction, and increased arterial stiffness and further lead to an imbalance in immune homeostasis and a persistent proinflammatory state, all of which are significant predictors of CVD and hypertension.

More importantly, developing effective dietary modification strategies tailored to the population is urgently needed to promote health.

Reference: Hyung-Suk Yoon, PhD, MPH; Qiuyin Cai, MD, PhD; Jae Jeong Yang, PhD, MPH; et al; Sodium Intake and Cause-Specific Mortality Among Predominantly Low-Income Black and White US Residents; Journal: JAMA Network Open; doi:10.1001/jamanetworkopen.2024.3802

Exercising 2-3 times a week linked to lower insomnia risk, finds study

A study published in the journal BMJ Open suggested that consistently exercising 2-3 times a week over the long term is linked to a lower current risk of insomnia as well as the ability to clock up the recommended 6-9 hours of sleep every night.

Regular exercise is associated with better overall health, and several studies have suggested that physical activity promotes better quality sleep and may improve symptoms of chronic insomnia, noted the researchers.

To explore this further, the researchers assessed the frequency, duration, and intensity of weekly physical activity and symptoms of insomnia, nightly sleep clocked up, and daytime sleepiness among middle-aged adults from 21 centres in nine European countries. The 4,399 study participants were drawn from the European Community Respiratory Health Survey and answered questions on the frequency and duration of physical activity at baseline and on physical activity, insomnia symptoms, sleep duration and daytime sleepiness.

The results revealed that over the 10 year period, 37% of participants were persistently inactive; 18% became physically active; 20% became inactive; and 25% were persistently active. Persistently active participants were more likely to be men, younger, and to weigh slightly less. They were also less likely to be current smokers and more likely to be currently working. After adjusting for age, sex, weight (BMI), smoking history, and study centre, those who were persistently active were significantly (42%) less likely to find it difficult to fall asleep, 22% less likely to have any symptoms of insomnia, and 40% less likely to report (37% less likely) insomnia symptoms.

The findings suggested that persistently active participants were significantly (55%) more likely to be normal sleepers and significantly less likely (29%) to be short (6 hours or less), and 52% less likely to be long, sleepers (9 hours or more). And those who became active were 21% more likely to be normal sleepers than those who were persistently inactive. As for total nightly hours of sleep and daytime sleepiness, after adjusting the demographics, persistently active participants were most likely to be normal sleepers while the persistently inactive were least likely to be in that category.

“Our results are in line with previous studies that have shown the beneficial effect of [physical activity] on symptoms of insomnia, but the current study additionally shows the importance of consistency in exercising over time, because the association was lost for initially active subjects who became inactive,” concluded the researchers.

Reference: Association between physical activity over a 10-year period and current insomnia symptoms, sleep duration and daytime sleepiness: a European population-based study; Journal: BMJ Open; DOI: 10.1136/bmjopen-2022-067197