Early menarche, irregular menstruation, menopause onset, and HRT – especially estrogen-only HRT: all appear to be linked with an increased risk of asthma.
In childhood, asthma risk is higher in boys than in girls. But this risk reverses in adulthood. Women have higher asthma Incidence and more severe symptoms than men.1 Is the reversal related to post-pubertal hormonal changes in women? It's known that early menarche and hormone replacement therapy (HRT) in postmenopausal women are linked to increased asthma risk.2, 3
In the most comprehensive meta-analysis of asthma in females, McCleary et al4 searched 11 databases and contacted experts for studies and conference abstracts published from 1990-2015. They included 64 studies covering 554,293 individuals.
• Meta-analyses were conducted for studies on menarche, menstruation, menopause, hormonal contraceptives, and HRT
• Analyses for HRT studies stratified by BMI and smoking
Compared to typical menarche (11-13 years):
. Early menarche (<11 yrs) was linked to 49% increased odds of new onset asthma
Compared to regular menstruation:
. Irregular menstruation was linked to 59% increased odds of asthma in the past year
Compared to pre-menopause:
. Onset of menopause was linked to 25% increased risk of current asthma
Compared to never use, ever, past, and current HRT use were linked to new onset asthma. Asthma risk was higher in normal weight and non-smoking women vs overweight/obese and smoking women.
A majority of studies in the meta-analysis had a moderate or high risk of bias and did not assess many outcomes. The lack of high quality studies limited ability to determine whether sex hormones cause asthma in women after puberty.
Among the unanswered questions is how estrogen metabolism influences asthma risk.
. Early menarche and irregular menstruation may indicate anovulation and unopposed estrogen; both linked to increased asthma risk
. Estrogen-only HRT linked to increased asthma risk
. Smoking may influence estrogen metabolism and was found to be protective
What can be gleaned from this meta-analysis? These key points.
. Early menarche, irregular menstruation, and onset of menopause were linked to increased risk of asthma
• HRT use, especially estrogen-only HRT, were linked to increased asthma risk in women
• Smoking and overweight-obesity appeared to be protective
Increased risk of asthma risk appears to be linked to early menarche, irregular menstruation, menopause onset, and HRT â especially estrogen-only HRT. Details here from the most comprehensive meta-analysis of asthma in females to date.
1. Nwaru BI, Nurmatov U, Sheikh A. Endogenous and exogenous sex steroid hormones in asthma and allergy in females: protocol for a systematic review and meta-analysis. NPJ Prim Care Respir Med. 2016; 26:15078. https://www.ncbi.nlm.nih.gov/pubmed/268206442. Lieberoth S, Gade EJ, Brok J, et al. Age at menarche and risk of asthma: systematic review and meta-analysis. J Asthma. 2014; 51:559-565. 3. Zemp E, Schikowski T, Dratva J, et al. Asthma and the menopause: a systematic review and meta-analysis. Maturitas. 2012; 73:212-217.4. McCleary N, Nwaru BI, Nurmatov UB, et al. Endogenous and exogenous sex steroid hormones in asthma and allergy in females: a systematic review and meta-analysis. J Allergy Clin Immunol. 2018 Jan 2. pii: S0091-6749(17)33009-9. doi: 10.1016/j.jaci.2017.11.034 https://www.ncbi.nlm.nih.gov/pubmed/29305316