Background In cross-sectional studies, elevated systolic blood pressure (SBP) is associated with increased left ventricular mass (LVM), which leads to increased cardiovascular morbidity and mortality. Current guidelines recommend a “watch and wait” approach in younger individuals with a borderline-high SBP. We investigated if this was a safe assumption.

Methods The Medical Research Council National Survey of Health and Development is a birth cohort study following men and women born in Britain in 1 week in March 1946. When study members were 60–64 years of age, 1700 underwent echocardiography and LVM indexed to body-surface-area (LVMI) was measured. The relationship between repeated measures of SBP and antihypertensive treatment (measured at 4 time points: ages 60–64 (current), 53, 43 and 36) and LVMI at 60–64 years was examined using sex-adjusted multiple regression models. Then, multilevel models of SBP were used to estimate person-specific intercepts (SBP at age 36) and slopes (rate of change in SBP between 36 and 53 years). The intercepts and slopes were then included in sex-adjusted linear regression models with LVMI as the outcome.

Results Individuals on treatment for hypertension, from age 43 years onwards, had higher mean LVMI than those who were not on treatment, irrespective of level of SBP at the same age. LVMI was 12.3 g/cm² (95% CI 9.2 to 15.4; p<0.001) higher for those currently on treatment, 10.0 g/cm² higher (95% CI 5.9 to 14.1; p<0.001) for those on treatment at age 53, and 15.1 g/cm² higher (95% CI 5.8 to 24.3; p=0.001) for treatment at age 43. In associated analyses, the effect of mid-life rate of change in SBP (from 36 to 53 years) on LVMI at age 60–64 years was 10 times greater than the effect of more recent rate of change in SBP (from 53 years to current).

Conclusions Our research suggests being on antihypertensive treatment may not normalise LVMI due to irreversible cardiac damage occurring in mid-life in poorly controlled hypertensives. Early identification and effective treatment of individuals with rapidly increasing SBP in mid-life may be key to preventing such damage. A review of current guidelines on monitoring and screening of blood pressure may thus be required.