Longer duration of breastfeeding appears to reduce the risk of recurrent cough in young adults, a study from the United States has found.

The researchers used data from the Tucson Children’s Respiratory Study, a large non-selected birth cohort in which infant feeding practices and adult health outcomes were ascertained prospectively.

This population, born in the 1980s, has been followed for more than 30 years. Detailed parental demography, education and health status were recorded at the outset.

Using questionnaires and data derived from regular physician checks, infant feeding practices were determined at regular intervals. Infants were categorised into those where formula was introduced: from birth or at less than one month of age;  between one and four months; and at four or more months.

Questionnaires were completed when the children reached 22, 26 and 32 years of age. Recurrent cough was defined as two or more episodes of cough without a cold that lasted for a week during the past year.

Participants were also asked about physician-diagnosed asthma, active smoking, heartburn, sinus trouble and allergic rhinitis. Adult body mass index (BMI) was calculated from self-reported height and weight at each age. Confounders were considered, in particular the known effect of breastfeeding on improving lung volume, so FVC was determined using lung function tests at each age. Potential early confounders such as RSV infection, bronchial hyperresponsiveness, atopy and early wheezing were also taken into account.

Of the original cohort, a total of 503 completed all three questionnaires, 163 completed two questionnaires and 120 completed one questionnaire.

Of the 786 participants, 19% breastfed for < 1 month, 50% for ≥ 1 to < 4 months and 31% for ≥ 4 months. The prevalence of recurrent cough at 22, 26 and 32 years was similar: 17%, 15% and 16% respectively. There was a significant protective relation between breastfeeding duration and recurrent cough between ages 22 and 32.

Each ordinal increase in breastfeeding duration was associated with a decreased risk of recurrent cough in adult life: adjusted OR 0.71 (95% CI: 0.56-0.89; P = 0.004).

Additional adjustment for concurrent adult asthma, wheeze, smoking and lung volume did not affect the results.

Essentially the study demonstrates improved respiratory health in young adulthood for breastfed individuals and identifies the need for further research to find if this has implications later in life.

The study authors conclude: ‘This analysis demonstrates a protective relation between breastfeeding in early life and recurrent cough at ages 22-32. Longer duration of breastfeeding is associated with a dose-related reduced prevalence of adult recurrent cough, suggesting potential long-term protective effects on respiratory health.’

‘Future research should consider relations of breastfeeding with adult symptoms and conditions, to ascertain whether this behaviour in early life is associated with alterations in adult health beyond the protection it provides in infancy,’ they add.

Dr Peter Saul

Gerhart KD, Stern DA, Guerra S et al. Protective effect of breastfeeding on recurrent cough in adulthood. Thorax 2018;73:833-39