Quantile-Specific Heritability may Account for Gene–Environment Interactions Involving Coffee Consumption

Estimated heritability of coffee intake ranges from 0.36 to 0.58, however, these point estimates assume that inherited effects are the same throughout the distribution of coffee intake, i.e., whether consumption is high or low relative to intake in the population. Quantile regression of 4788 child–parent pairs and 2380 siblings showed that offspring–parent and sibling concordance became progressively greater with increasing quantiles of coffee intake. Each cup/day increase in the parents’ coffee intake was associated with an offspring increase of 0.020 ± 0.013 cup/day at the 10th percentile of the offsprings’ coffee intake (slope ± SE, NS), 0.137 ± 0.034 cup/day at their 25th percentile (P = 5.2 × 10–5), 0.159 ± 0.029 cup/day at the 50th percentile (P = 5.8 × 10–8), 0.233 ± 0.049 cup/day at the 75th percentile (P = 1.8 × 10–6), and 0.284 ± 0.054 cup/day at the 90th percentile (P = 1.2 × 10–7). This quantile-specific heritability suggests that factors that distinguish heavier vs. lighter drinkers (smoking, male sex) will likely manifest differences in estimated heritability, as reported.