Table 1.
Subject characteristics (n=502 489)
| Variable | Percentage or mean (SD)* | Mean (SD) of frailty index† | Bivariate association with frailty index‡ |
| Frailty index, mean (SD) | 0.14 (0.08) | ||
| Early life factors | |||
| Maternal smoking around birth, % | P<0.0001 | ||
| No | 70.75% | 0.133 (0.073) | |
| Yes | 29.25% | 0.146 (0.078) | |
| Breast fed as a baby, % | P<0.0001 | ||
| No | 27.65% | 0.137 (0.076) | |
| Yes | 72.35% | 0.134 (0.074) | |
| Birth weight, % | P<0.0001 | ||
| Low birth weight | 10.26% | 0.149 (0.080) | |
| Normal birth weight | 76.34% | 0.131 (0.073) | |
| High birth weight | 13.40% | 0.136 (0.076) | |
| Birth month, % | P=0.0002 | ||
| January | 8.44% | 0.138 (0.076) | |
| February | 7.96% | 0.137 (0.075) | |
| March | 8.98% | 0.138 (0.075) | |
| April | 8.59% | 0.139 (0.076) | |
| May | 8.98% | 0.138 (0.076) | |
| June | 8.45% | 0.139 (0.076) | |
| July | 8.48% | 0.139 (0.076) | |
| August | 8.24% | 0.138 (0.076) | |
| September | 8.14% | 0.138 (0.075) | |
| October | 8.06% | 0.137 (0.076) | |
| November | 7.63% | 0.137 (0.075) | |
| December | 8.03% | 0.138 (0.076) | |
| Perinatal diseases, % | P<0.0001 | ||
| No | 99.82% | 0.138 (0.075) | |
| Yes | 0.18% | 0.149 (0.084) | |
| Born in the UK, % | P=0.0381 | ||
| No | 8.96% | 0.137 (0.076) | |
| Yes | 91.04% | 0.138 (0.075) | |
| Sociodemographics | |||
| Age (years), mean (SD) | 56.53 (8.10) | r=0.16, p<0.0001 | |
| Gender, % | P<0.0001 | ||
| Female | 54.40% | 0.141 (0.075) | |
| Male | 45.60% | 0.134 (0.076) | |
| Ethnicity, % | P<0.0001 | ||
| Other | 5.41% | 0.141 (0.078) | |
| Caucasian | 94.59% | 0.138 (0.075) | |
| Education, % | P<0.0001 | ||
| Less than college | 67.27% | 0.145 (0.077) | |
| College or university degree | 32.73% | 0.122 (0.069) | |
| Health behaviours | |||
| Moderate or vigorous physical activity, % | P<0.0001 | ||
| None | 10.75% | 0.160 (0.085) | |
| 1 day | 7.11% | 0.134 (0.072) | |
| 2 days | 13.40% | 0.133 (0.072) | |
| 3 days or more | 68.75% | 0.135 (0.073) | |
| Current alcohol consumption, % | P<0.0001 | ||
| No | 8.08% | 0.166 (0.088) | |
| Yes | 91.92% | 0.135 (0.074) | |
| Current smoking, % | P<0.0001 | ||
| No | 89.39% | 0.135 (0.074) | |
| Yes | 10.61% | 0.159 (0.084) |
*Presented are means (SD) for continuous variables and percentages for categorical variables. The maternal smoking variable includes 13.86% missing data, the breast fed as a baby variable includes 23.64% missing data, the birth weight variable includes 44.88% missing data, the education variable includes 2.02% missing data and the moderate or vigorous physical activity variable includes 2.43% missing data.
†Presented are the means (SD) of the frailty index per group.
‡Bivariate analyses are unpaired t-tests for binary variables, analysis of variance for ordinal variables and Pearson’s correlation for continuous variables.