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Low Birth Weight Linked to Increased COPD Risk

Key Takeaways

  • Lower birth weight is linked to increased COPD risk, especially among smokers, highlighting the importance of early-life factors in COPD development.
  • The study utilized the UK Biobank, analyzing over 250,000 participants, and adjusted for demographic, health, and lifestyle factors to assess COPD risk.
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Low birth weight is associated with an increased risk of chronic obstructive pulmonary disease (COPD), particularly among smokers, highlighting the impact of early-life factors on respiratory health.

Lower birth weight may increase the risk of chronic obstructive pulmonary disease (COPD), according to a study published in BMJ Open Respiratory Research.1

The researchers emphasized the importance of searching for COPD's potential causes to reduce the mortality rate, with smoking considered the most common traditional risk factor. However, others are becoming increasingly recognized worldwide, demonstrating that COPD's etiology is still not fully discovered.

Some evidence has suggested that birth weight is associated with abnormal lung function and has been considered one of the underlying factors of COPD. Consequently, the latest edition of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) COPD strategy included the belief that low birth weight will affect normal airway development and cause lung dysfunction.

However, there is a lack of sufficient population studies to explain the relationship between birth weight and COPD. Therefore, the researchers conducted a prospective analysis using the UK Biobank to investigate this relationship.

sleeping baby in father's arms | Image Credit: BazziBa - stock.adobe.com

Low birth weight is associated with an increased risk of chronic obstructive pulmonary disease (COPD), particularly among smokers. | Image Credit: BazziBa - stock.adobe.com

The UK Biobank is a large prospective cohort study of over 500,000 participants aged between 40 and 69 years from 22 assessment centers throughout the United Kingdom.2 Participants provided demographic, health, and lifestyle data via interviews and underwent standardized physical exams.

During the baseline survey, participants recalled their birth weight.1 The baseline body mass index was defined as baseline weight divided by the square of baseline height. Additionally, the researchers identified COPD diagnoses using the electronic health record linkage to the UK National Health Service register.

Baseline continuous variables were described as means (standard deviations [SDs]), and categorical variables were expressed as constituent ratios (n, %). Follow-up time was calculated from the baseline investigation date to the first COPD diagnosis, last follow-up date, loss of follow-up, or death, whichever came first.

Also, Cox proportional hazards regression models estimated HRs for the association between birth weight and COPD risk, with birth weight divided into quintiles (Q1, < 2.86 kg; Q2, 2.86-3.18 kg; Q3, 3.18-3.40 kg; Q4, 3.40-3.80 kg; Q5, ≥ 3.80); Q3 was the reference group.

The researchers built 3 multivariable models to analyze the results, adjusting for demographic, health, and lifestyle factors. Model 1 was adjusted for baseline age, sex, and race; model 2 was further adjusted by factors like physical activity, smoking status, and family history of respiratory diseases; and model 3 was adjusted for early life factors (birthplace, maternal smoking, multiple births, and breastfeeding).

They excluded 49,724 participants from the UK Biobank with baseline airway obstruction and 201,517 others who withdrew (n = 44) or had missing birth weight data (n = 201,473). Consequently, the study population consisted of 251,172 participants.

During a median follow-up of 12.3 years (IQR, 11.3-13.2), 5601 patients with COPD were discovered among the study population. Overall, the median birth weight was 3.32 kg (IQR, 2.95-3.66). As for covariates, the proportion of maternal smoking was the highest in the lowest birth weight group (Q1) and decreased with increasing birth weight (Q2-Q5, 26.42%-22.72%, respectively). Also, those with lower birth weight were more likely to be female (Q1, 71.91%; Q2, 65.96%).

Compared with the reference group, Q1 had a higher COPD risk in all 3 models (model 1: [HR, 1.37; 95% CI, 1.26-1.49]; model 2: [HR, 1.24; 95% CI, 1.14-1.35]; model 3: [HR, 1.21; 95% CI, 1.11-1.32], respectively). Q5 also showed a positive association with COPD risk in model 1, but this was not found in model 2 (HR, 1.05; 95% CI, 0.96-1.14) or 3 (HR, 1.05; 95% CI, 0.96-1.15).

In terms of smoking, there was a significant association among current smokers with COPD risk and low birth weight (Q1 vs Q3: HR, 1.25; 95% CI, 1.13-1.38). Also, the study found a non-linear relationship between birth weight and COPD risk, with lower birth weight associated with higher risk, particularly in smokers (P < .001). This trend was confirmed by adjusting for various factors, like socioeconomic status, lifestyle, and birth-related conditions.

The relationship between COPD risk and birth weight remained consistent, even after excluding participants with early COPD diagnosis (n = 405; HR, 1.21; 95% CI, 1.11-1.32), poor self-rated health (n = 8816; HR, 1.18; 95% CI, 1.08-1.30), baseline asthma (n = 26,405; HR, 1.20; 95% CI, 1.09-1.32), or multiple births (n = 8914; HR, 1.20; 95% CI, 1.09-1.31). Therefore, the relationship is robust and not driven by these factors.

Lastly, the researchers acknowledged their limitations, including the risk of misclassification due to relying on diagnostic codes to identify patients with COPD. However, they expressed confidence in their findings and used them to suggest future ways to reduce COPD risk.

“We should focus on the effect of early-life exposure for reducing COPD risk and ensuring life quality in the early period of humans,” the authors concluded.

References

  1. Luo P, He J, Wan X, et al. Association between birth weight and chronic obstructive pulmonary disease in the UK Biobank: a prospective cohort study. BMJ Open Respir Res. 2024;11(1):e002366. doi:10.1136/bmjresp-2024-002366
  2. Du W, Guan H, Wan X, et al. Circulating liver function markers and the risk of COPD in the UK Biobank. Front Endocrinol (Lausanne). 2023;14:1121900. doi:10.3389/fendo.2023.1121900
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