Trends in the association of parental history of obesity over 60 years

Objective The association of familial as compared to genetic factors in the current obesogenic environment, compared with earlier, leaner time periods, is uncertain. Methods Participants from the Framingham Heart Study were classified according to parental obesity status in the Original, Offspring, and Third Generation cohorts; mean BMI levels were estimated and we compared the association of parental history across generations. Finally, a genetic risk score comprised of 32 well-replicated single nucleotide polymorphisms for BMI was examined in association with BMI levels in 1948, 1971, and 2002. Results BMI was 1.49 kg/m² higher per each affected parent among the Offspring, and increased to 2.09 kg/m² higher among the Third Generation participants (P-value for the cohort comparison=0.007). Parental history of obesity was associated with increased weight gain (P < 0.0001) and incident obesity (P = 0.009). Despite a stronger association of parental obesity with offspring BMI in more contemporary time periods, we observed no change in the effect size of a BMI genetic risk score from 1948 to 2002 (P = 0.11 for test of trend across the time periods). Conclusions The association of parental obesity has become stronger in more contemporary time period, whereas the association of a BMI genetic risk score has not changed.