As shown in Table 1, we observed sex differences in the left-hand fingertip features.
Table 1
Comparison of the fingertip characteristics in 62 healthy subjects according to sex
| length [cm] | area [cm2] |
mean (SD) | sex differences | mean (SD) | sex differences |
thumb | M | 3.17 (0.23) | p < 0.001 (t = 6.42) | 6.40 (0.78) | p < 0.001 (U = 67.00) |
F | 2.84 (0.16) | 5.01 (0.53) |
index finger | M | 2.63 (0.17) | p < 0.001 (t = 6.01) | 4.17 (0.51) | p < 0.001 (t = 7.38) |
F | 2.38 (0.15) | 3.38 (0.32) |
middle finger | M | 2.74 (0.16) | p < 0.001 (t = 7.17) | 4.41 (0.51) | p < 0.001 (t = 8.22) |
F | 2.46 (0.15) | 3.49 (0.35) |
ring finger | M | 2.70 (0.18) | p < 0.001 (U = 123.00) | 4.03 (0.49) | p < 0.001 (t = 6.95) |
F | 2.43 (0.17) | 3.25 (0.39) |
little finger | M | 2.47 (0.17) | p < 0.001 (t = 6.32) | 3.40 (0.39) | p < 0.001 (t = 7.60) |
F | 2.19 (0.19) | 2.66 (0.37) |
M: males (N = 31); F: females ( N = 31); SD: standard deviation |
Figure 1(a) represents the distribution of CPT values obtained from each left fingertip according to sex. As a result of having transformed these CPTs into log values, the males’ log-transformation values for fingertips from the thumb to the little finger were − 0.02, − 0.12, − 0.10, − 0.11, and − 0.12; the females’ results were − 0.21, − 0.28, − 0.28, − 0.30, and − 0.31. The log-transformation values showed sex differences among all fingers: thumb: t(45.02) = 5.82, p < 0.001; index finger: t(48.93) = 3.91, p < 0.001; middle finger: U(62) = 196.50, p < 0.001; ring finger: U(62) = 155.50, p < 0.001; little finger: U(62) = 169.00, p < 0.001. Figure 1(b) shows the relationship between the CPT values and the fingertip characteristics for all participants. As a result of having analyzed the data using Spearman’s correlations, a statistically positive correlation was observed between the CPT values and fingertip length (ρ = 0.44, p < 0.001). Similarly, the relation between the CPT values and the fingertip area was found to have a statistically positive correlation, and the Spearman’s correlation coefficient (ρ) was 0.47 (p < 0.001).
Figure 2(a) represents the CPT value results from 15 males with short fingertips and 15 females with long fingertips. The difference in average fingertip length between the two groups was not statistically significant: thumb, U(30) = 98.00, p = 0.548; index finger, U(30) = 107.50, p = 0.836; middle finger, U(30) = 76.00, p = 0.130; ring finger, t(28) = 0.052, p = 0.959; little finger, U(30) = 76.00, p = 0.130. Despite adjusting for fingertip length, we observed sex differences between the two groups as shown in the log-transformed adjusted CPT values: thumb, t(20.05) = 3.493, p = 0.002; middle finger, U(30) = 44.50, p = 0.005; ring finger, t(30) = 55.50, p = 0.018; little finger, U(30) = 30.00, p = 0.001. There was no significant difference between the groups for the index finger (t(21.47) = 1.96, p = 0.063). Figure 2(b) shows the CPT value results from 10 males with each small fingertip area and 10 females with each large fingertip area. The difference in average fingertip area between the two groups was not statistically significant: thumb: U(20) = 39.00, p = 0.406; index finger: U(20) = 39.00, p = 0.406; middle finger: U(20) = 35.00, p = 0.257; ring finger: U(20) = 40.00, p = 0.450; little finger: U(20) = 44.00, p = 0.650. Despite adjusting for fingertip area, we observed sex differences in three fingertips between the two groups as shown in the log-transformed adjusted CPT values: thumb, t(18) = 2.649, p = 0.016; middle finger, U(20) = 12.00, p = 0.004; ring finger, t(18) = 2.206, p = 0.041.