Objectives: Although lung function decline is a normal ageing process, it can be potentiated by risk factors. However, the potential impact of early life factors on lung function decline has been scarcely studied. The aim of this study was to investigate the potential correlation between birth season and adult lung function. Methods: We enrolled 1008 South Korean patients (530 men and 478 women; age range, 40 - 80 years) who were hospitalized for urological surgery, irrespective of respiratory disease. All patients underwent the pulmonary function test before any surgery or procedure. Based on their birth season, the patients were divided into two groups (spring, summer, and fall vs. winter). Results: Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1 % predicted of men born in winter were lower than those of men born in other seasons. Univariate and multivariate analyses using linear regression models also showed that birth season was a significant predictive factor for FVC, FEV1, and FEV1 % predicted in men. However, birth season was not correlated with lung function in women. Among male ever-smokers, FEV1 and FEV1 % predicted were lower for men born in winter than for those born in other seasons. Conclusions: Unlike women, men born in winter had lower lung function than did men born in other seasons. These results suggest that birth season might be an early life factor that predicts airway function. Furthermore, birth season has different effects on adult lung function depending on the patient’s sex.
Chronic obstructive pulmonary disease (COPD) is set to become the third most important cause of death worldwide [
An increasing body of evidence suggests that COPD is not simply a disease of old age that is largely restricted to heavy smokers, but may be associated with insults to the developing lung during fetal life and the first few years of postnatal life, when lung growth and development are rapid [
To date, the potential impact of birth season as an early life factors on lung function has been scarcely studied. The aim of this study was to investigate the potential correlation between birth season (month of birth) and adult lung function.
The study was approved by the Gachon University Gil Hospital Institutional Review Board (GCIRB2016-107). A total of 1008 South Korean patients (530 men and 478 women; age range, 40 - 80 years) who were hospitalized for urological surgery at a single tertiary academic center were enrolled in our investigation irrespective of respiratory disease. Based on the smoking histories, “never- smokers” were defined as those who had smoked on average <1 cigarette/day for <6 months or had never smoked. For the “ever-smokers”, pack-years were calculated to quantify tobacco use, with 1 pack-year being equivalent to smoking an average of 20 cigarettes/day for 1 year.
All 1008 patients underwent spirometry before undergoing any operation or procedure. The tests were performed according to the American Thoracic Society guidelines [
We recorded the patients’ birth seasons based on their birth months as follows: spring (March-May), summer (June-August), fall (September-November), and winter (December-February, mean temperature of January in Korea: −6˚C - 3˚C). Comparisons were performed between patients born in winter and those born in other seasons.
The relationships between the study variables were analyzed using Pearson’s linear correlation. To identify the independent predictive factors influencing lung function, we performed univariate and multivariate analyses using linear regression modeling. Student’s t-test was used to compare variables between the two study groups according to birth seasons (i.e., spring, summer, and fall vs. winter) and sex. All analyses were performed using SPSS 12.0 (SPSS Inc., Chicago, IL, USA) and p < 0.05 was considered statistically significant.
Characteristics of all 1008 patients are summarized in
Men (N = 530) | Women (N = 478) | p-value | |
---|---|---|---|
Mean ± SD | Mean ± SD | ||
Age (years) | 68.4 ± 7.0 | 67.6 ± 7.2 | 0.08 |
Height (cm) | 166.8 ± 5.9 | 153.6 ± 6.0 | <0.05 |
Weight (kg) | 65.6 ± 9.0 | 58.6 ± 9.2 | <0.05 |
BMI (kg/m2) | 23.5 ± 2.7 | 24.8 ± 3.6 | <0.05 |
FVC (L) | 3.60 ± 0.68 | 2.48 ± 0.46 | <0.05 |
FEV1 (L) | 2.60 ± 0.63 | 1.96 ± 0.40 | <0.05 |
FEV1/FVC (%) | 71.9 ± 10.3 | 78.9 ± 6.8 | <0.05 |
predFVC (%) | 95.6 ± 16.3 | 94.1 ± 17.1 | 0.15 |
predFEV1 (%) | 99.8 ± 22.1 | 102.6 ± 22.5 | 0.05 |
Smoking (PY) | 14.4 ± 20.8 | 0.6 ± 4.0 | <0.05 |
Smoker (%) | 46.4% (246/530) | 3.1% (15/478) | <0.05 |
Smoking of smoker (PY) | 32.7 ± 19.6 | 19.0 ± 12.8 | <0.05 |
FEV1/FVC < 70 (%) | 32.6% (173/530) | 7.3% (35/478) | <0.05 |
Abbreviations: BMI, Body mass index; FVC, Forced vital capacity; FEV1, Forced expiratory volume in 1 second; predFVC, FVC % predicted; predFEV1, FEV1 % predicted; PY, pack-years.
FEV1 % predicted of men born in winter was lower than that of women born in winter (96.3 ± 21.9 vs. 104.3 ± 20.1, p < 0.05) (
FVC, FEV1, and FEV1 % predicted of men born in winter were lower than those of men born in other seasons (
Univariate analysis using linear regression models showed that birth season was a significant predictive factor for FVC, FEV1, and FEV1 % predicted in men (FVC: r = 0.090, p < 0.05 ; FEV1: r = 0.104, p < 0.05; FEV1 % predicted: r = 0.105, p < 0.05) (
Out of the 530 men, 246 (46.4%) were ever-smokers; mean smoking exposures
Spring, summer, and fall | Winter | p-value | ||
---|---|---|---|---|
Male | N | 371 | 159 | |
Age (years) | 68.4 ± 7.3 | 68.5 ± 6.3 | 0.85 | |
Height (cm) | 166.9 ± 6.1 | 166.7 ± 5.3 | 0.62 | |
Weight (kg) | 65.6 ± 9.2 | 65.3 ± 8.6 | 0.73 | |
BMI (kg/m2) | 23.5 ± 2.8 | 23.5 ± 2.6 | 0.92 | |
FVC (L) | 3.64 ± 0.70 | 3.51 ± 0.63 | <0.05 | |
FEV1 (L) | 2.64 ± 0.64 | 2.50 ± 0.61 | <0.05 | |
FEV1/FVC (%) | 72.3 ± 10.0 | 70.9 ± 10.8 | 0.15 | |
predFVC (%) | 96.4 ± 16.6 | 93.7 ± 15.6 | 0.08 | |
predFEV1 (%) | 101.3 ± 22.0 | 96.3 ± 21.9 | <0.05 | |
Smoking (PY) | 14.7 ± 21.8 | 13.8 ± 18.1 | 0.64 | |
Smoker (%) | 45.3% (168/371) | 49.1% (78/159) | 0.43 | |
FEV1/FVC < 70 (%) | 32.1% (119/371) | 34.0% (54/159) | 0.67 | |
Female | N | 361 | 117 | |
Age (years) | 67.8 ± 6.9 | 67.0 ± 8.2 | 0.37 | |
Height (cm) | 153.7 ± 6.0 | 153.5 ± 5.8 | 0.86 | |
Weight (kg) | 58.5 ± 9.1 | 58.8 ± 9.4 | 0.75 | |
BMI (kg/m2) | 24.8 ± 3.6 | 25.0 ± 3.9 | 0.60 | |
FVC (L) | 2.47 ± 0.46 | 2.51 ± 0.44 | 0.44 | |
FEV1 (L) | 1.95 ± 0.40 | 1.99 ± 0.38 | 0.28 | |
FEV1/FVC (%) | 78.7 ± 6.9 | 79.5 ± 6.5 | 0.28 | |
predFVC (%) | 93.8 ± 17.5 | 95.0 ± 15.5 | 0.51 | |
predFEV1 (%) | 102.0 ± 23.2 | 104.3 ± 20.1 | 0.33 | |
Smoking (PY) | 0.7 ± 4.4 | 0.2 ± 1.9 | 0.10 | |
Smoker (%) | 3.3% (12/361) | 2.6% (3/117) | 0.68 | |
FEV1/FVC < 70 (%) | 7.2% (26/361) | 7.7% (9/117) | 0.86 |
Abbreviations: BMI, Body mass index; FVC, Forced vital capacity; FEV1, Forced expiratory volume in 1 second; predFVC, FVC % predicted; predFEV1, FEV1 % predicted; PY, pack-years; Spring, March-May; Summer, June-August; Fall, September-November; Winter, December-February.
of all men and male ever-smokers were 14.4 ± 20.8 and 32.7 ± 19.6 pack-years, respectively. However, out of the 478 women, only 15 (3.1%) were ever-smokers; mean smoking exposure of all women and female ever-smokers were 0.6 ± 4.0 and 19.0 ± 12.8 pack-years, respectively (
When the patients were divided into two groups based on birth season, among the male ever-smokers (N = 246), lung functions (FEV1 and FEV1 % predicted) were lower in men born in winter than in those born in other seasons (
FVC | FEV1 | FEV1/FVC | predFVC | predFEV1 | |||
---|---|---|---|---|---|---|---|
Men | Age | r | −0.315 | −0.413 | −0.273 | 0.011 | −0.001 |
p | <0.05 | <0.05 | <0.05 | 0.80 | 0.98 | ||
Height | r | 0.424 | 0.347 | 0.023 | −0.051 | −0.019 | |
p | <0.05 | <0.05 | 0.60 | 0.25 | 0.67 | ||
Weight | r | 0.233 | 0.266 | 0.152 | −0.097 | 0.007 | |
p | <0.05 | <0.05 | <0.05 | <0.05 | 0.88 | ||
BMI | r | 0.015 | 0.102 | 0.168 | −0.085 | 0.022 | |
p | 0.74 | <0.05 | <0.05 | 0.05 | 0.62 | ||
Smoking | r | −0.093 | −0.218 | −0.261 | −0.040 | −0.185 | |
p | <0.05 | <0.05 | <0.05 | 0.37 | <0.05 | ||
Birth season | r | 0.090 | 0.104 | 0.063 | 0.076 | 0.105 | |
p | <0.05 | <0.05 | 0.15 | 0.08 | <0.05 | ||
Women | Age | r | −0.386 | −0.430 | −0.176 | 0.065 | 0.151 |
p | <0.05 | <0.05 | <0.05 | 0.16 | <0.05 | ||
Height | r | 0.519 | 0.494 | 0.054 | −0.147 | −0.204 | |
p | <0.05 | <0.05 | 0.24 | <0.05 | <0.05 | ||
Weight | r | 0.160 | 0.188 | 0.106 | −0.186 | −0.139 | |
p | <0.05 | <0.05 | <0.05 | <0.05 | <0.05 | ||
BMI | r | −0.103 | −0.060 | 0.086 | −0.127 | −0.047 | |
p | <0.05 | 0.19 | 0.06 | <0.05 | 0.30 | ||
Smoking | r | −0.097 | −0.147 | −0.185 | −0.125 | −0.158 | |
p | <0.05 | <0.05 | <0.05 | <0.05 | <0.05 | ||
Birth season | r | −0.035 | −0.050 | −0.050 | −0.030 | −0.044 | |
p | 0.44 | 0.28 | 0.28 | 0.51 | 0.33 |
Abbreviations: BMI, Body mass index; FVC, Forced vital capacity; FEV1, Forced expiratory volume in 1 second; predFVC, FVC % predicted; predFEV1, FEV1 % predicted; Smoking, pack-years; Birth season, Spring, Summer, and Fall vs. Winter. r: Pearson correlation coefficient.
In the present study, we found that FEV1 % predicted was lower in men born in winter than in those born in other seasons (spring, summer, and fall), suggesting that the birth season as an early life factor somehow affects adult lung function
FVC | FEV1 | FEV1/FVC | predFVC | predFEV1 | |||
---|---|---|---|---|---|---|---|
Men | Age | β | −0.255 | −0.344 | −0.234 | 0.001 | 0.024 |
p | <0.05 | <0.05 | <0.05 | 0.99 | 0.60 | ||
Height | β | 0.392 | 0.256 | −0.090 | −0.011 | −0.034 | |
p | <0.05 | <0.05 | 0.07 | 0.84 | 0.51 | ||
Weight | β | −0.046 | 0.031 | 0.131 | −0.116 | −0.006 | |
p | 0.33 | 0.49 | <0.05 | <0.05 | 0.91 | ||
Smoking | β | −0.054 | −0.168 | −0.228 | −0.055 | −0.192 | |
p | 0.17 | <0.05 | <0.05 | 0.22 | <0.05 | ||
Birth season | β | 0.080 | 0.094 | 0.061 | 0.076 | 0.103 | |
p | <0.05 | <0.05 | 0.14 | 0.08 | <0.05 | ||
Women | Age | β | −0.272 | −0.325 | −0.170 | 0.018 | 0.101 |
p | <0.05 | <0.05 | <0.05 | 0.69 | <0.05 | ||
Height | β | 0.476 | 0.424 | −0.017 | −0.080 | −0.146 | |
p | <0.05 | <0.05 | 0.73 | 0.11 | <0.05 | ||
Weight | β | −0.068 | −0.030 | 0.080 | −0.157 | −0.073 | |
p | 0.09 | 0.45 | 0.10 | <0.05 | 0.13 | ||
Smoking | β | −0.111 | −0.160 | −0.184 | −0.127 | −0.154 | |
p | <0.05 | <0.05 | <0.05 | <0.05 | <0.05 | ||
Birth season | β | −0.022 | −0.031 | −0.031 | −0.026 | −0.041 | |
p | 0.55 | 0.40 | 0.48 | 0.56 | 0.36 |
Abbreviations: BMI, Body mass index; FVC, Forced vital capacity; FEV1, Forced expiratory volume in 1 second; predFVC, FVC % predicted; predFEV1, FEV1 % predicted; Smoking, pack-years; Birth season, Spring, Summer, and Fall vs. Winter. β: Standardized coefficient beta.
depending on an individual’s sex. Our finding also agrees with those of the two recent European multi-center cohort studies, which showed an association between lung function decline and birth season [
Early childhood is a critical time window for subsequent lung health. Adverse childhood environmental exposures can restrain growth [
Spring, summer, and fall | Winter | p-value | |||
---|---|---|---|---|---|
Never-smoker | Male | N | 203 | 81 | |
(N = 284) | Age (years) | 68.2 ± 7.4 | 68.4 ± 5.7 | 0.79 | |
Height (cm) | 167.0 ± 6.0 | 167.0 ± 5.4 | 0.98 | ||
Weight (kg) | 66.5 ± 9.4 | 66.7 ± 8.6 | 0.87 | ||
BMI (kg/m2) | 23.8 ± 2.7 | 23.9 ± 2.5 | 0.84 | ||
FVC (L) | 3.65 ± 0.70 | 3.52 ± 0.59 | 0.16 | ||
FEV1 (L) | 2.70 ± 0.62 | 2.60 ± 0.58 | 0.21 | ||
FEV1/FVC (%) | 74.0 ± 9.2 | 73.5 ± 9.1 | 0.64 | ||
predFVC (%) | 96.2 ± 16.9 | 93.6 ± 14.2 | 0.22 | ||
predFEV1 (%) | 103.5 ± 22.1 | 100.3 ± 21.0 | 0.27 | ||
FEV1/FVC < 70 (%) | 24.6% (50/203) | 24.7% (20/81) | 0.99 | ||
Female | N | 349 | 114 | ||
(N = 463) | Age (years) | 67.9 ± 6.8 | 67.0 ± 8.2 | 0.28 | |
Height (cm) | 153.5 ± 5.9 | 153.5 ± 5.8 | 0.10 | ||
Weight (kg) | 58.5 ± 9.1 | 58.9 ± 9.5 | 0.72 | ||
BMI (kg/m2) | 24.8 ± 3.5 | 25.0 ± 3.9 | 0.63 | ||
FVC (L) | 2.47 ± 0.46 | 2.50 ± 0.44 | 0.56 | ||
FEV1 (L) | 1.96 ± 0.39 | 1.99 ± 0.38 | 0.43 | ||
FEV1/FVC (%) | 79.0 ± 6.7 | 79.5 ± 6.5 | 0.46 | ||
predFVC (%) | 94.2 ± 17.5 | 94.8 ± 15.7 | 0.74 | ||
predFEV1 (%) | 102.8 ± 22.9 | 104.2 ± 20.3 | 0.57 | ||
FEV1/FVC < 70 (%) | 6.6% (23/349) | 7.9% (9/114) | 0.63 | ||
Ever-smoker | Male | N | 168 | 78 | |
(N = 246) | Age (years) | 68.6 ± 7.1 | 68.6 ± 7.0 | 1.00 | |
Height (cm) | 166.9 ± 6.2 | 166.3 ± 5.3 | 0.48 | ||
Weight (kg) | 64.6 ± 8.8 | 63.9 ± 8.4 | 0.58 | ||
BMI (kg/m2) | 23.2 ± 2.7 | 23.1 ± 2.6 | 0.84 | ||
FVC (L) | 3.64 ± 0.71 | 3.50 ± 0.67 | 0.14 | ||
FEV1 (L) | 2.57 ± 0.65 | 2.39 ± 0.62 | <0.05 | ||
FEV1/FVC (%) | 70.3 ± 10.5 | 68.3 ± 11.9 | 0.18 | ||
predFVC (%) | 96.6 ± 16.2 | 93.8 ± 17.1 | 0.21 | ||
predFEV1 (%) | 98.7 ± 21.6 | 92.1 ± 22.2 | <0.05 | ||
Smoking (PY) | 34.2 ± 21.1 | 29.5 ± 15.5 | 0.09 | ||
FEV1/FVC < 70 (%) | 41.1% (69/168) | 43.6% (34/78) | 0.71 |
Abbreviations: BMI, Body mass index; FVC, Forced vital capacity; FEV1, Forced expiratory volume in 1 second; predFVC, FVC % predicted; predFEV1, FEV1 % predicted; PY, pack-years; Spring, March-May; Summer, June-August; Fall, September-November; Winter, December-February.
were associated with more rapid lung function decline, whereas early day-care attendance, the presence of older siblings, and childhood pet keeping appeared to be associated with a less rapid decline. Moreover, similar to our patients, the participants in those studies who were born in the winter months had a more rapid decline in lung function than did those born in the other months. Being born in winter has been related to in utero exposures to viral infections or allergens and to a higher frequency of respiratory infections in the first months of life, both of which probably are major influences on the subsequent establishment of immune response [
The sex of an individual plays a major role in both the healthy and diseased lung from very early life onwards. Sex hormones exert regulatory effects on lung development, physiology, and pathology [
Smoking is known as the main risk factor for accelerated lung function decline in adults; however, the mechanisms underlying the variations in susceptibility to tobacco exposure between individuals are not well understood. In our study, lung function decline was more pronounced in male smokers who were born during winter than in those born during other seasons. This indicates that susceptibility to lung insults in later adulthood might be programmed early in life. When the patients were divided into two groups based on birth season (winter vs. spring, summer, and fall), among male ever-smokers (N = 246), lung functions (FEV1 and FEV1 % predicted) were lower in men born in winter than in those born in other seasons (spring, summer, and fall). This means that if a man born in winter smoke, he will have lower lung function than those born in other seasons. However, among male and female never-smokers, lung functions were not different between the two groups based on birth season. A synergistic effect of parental smoking has been described by Guerra et al. [
Investigating early life factors and their potential interactions requires large study populations; however, we enrolled patients from a very specific demographic group, thus limiting the generalizability of our observations to other populations. Therefore, we investigated only birth season, sex, and smoking exposure and did not investigate other early life factors such as fetal and early infant growth patterns, preterm birth, maternal obesity, diet and smoking, children’s diet, allergen exposure and respiratory tract infections, and genetic susceptibility. Another limitation of our study was the use of pre-bronchodilator spirometric values for evaluating lung function. Because of the lack of post-bron- chodilator measurements, we could not rule out some cases of transient airflow obstruction. Another limitation, as we discussed above, was the relatively small number of female smokers in our study group, which made it difficult to evaluate the correlation between birth season and smoking in women.
Our study demonstrated that unlike female patients, male patients born during winter had lower lung function than did those born in other seasons. These results suggest that birth season might be a predictor of lung function as an early life factor. Furthermore, birth season has different effects on adult lung function depending on the patient’s sex.
There are no conflicts of interest among the authors.
Kim, T.B. and Park, I-N. (2017) Do Birth Season and Sex Affect Adult Lung Function as Early Life Factors? Health, 9, 223-236. https://doi.org/10.4236/health.2017.92015