Demographic and clinical characteristics of subjects with genotypes across quintiles of serum surfactant protein D (SP-D) in the Lung Health Study
| Quintile | ||||||
| 1 | 2 | 3 | 4 | 5 | p-value | |
| Subjects | 786 | 792 | 812 | 822 | 829 | |
| SP-D ng·mL−1 | ≤59.7 | 59.7–81.3 | 81.3–105.4 | 105.4–139.5 | >139.5 | |
| Age years | 52.1±6.8 | 52.8±6.8 | 54.0±6.6 | 53.8±6.6 | 55.1±6.3 | <0.0001 |
| Males % | 63.6 | 65.5 | 61.6 | 62.2 | 63.1 | 0.524 |
| BMI kg·m−2 | 27.9±4.3 | 27.4±4.4 | 26.8±4.3 | 26.4±4.2 | 26.0±4.2 | <0.0001 |
| Smokers# % | 70.9 | 78.7 | 82.9 | 87.2 | 92.5 | <0.0001 |
| FEV1 % predicted | 78.5±11.6 | 75.7±12.0 | 74.9±12.0 | 74.6±11.9 | 73.3±12.2 | <0.0001 |
Data are presented as n, range or mean±sd, unless otherwise stated. p-values were generated using ANOVA for continuous variables and a Chi-squared test for categorical variables. BMI: body mass index; FEV1: forced expiratory volume in 1 s. #: either continuous or intermittent smokers, defined as smokers (verified objectively using salivary cotinine or exhaled carbon monoxide) at the time of at least one annual follow-up visit. All values are for the year 5 values because this was the visit during which blood samples were collected.