UNDERSTANDING HEALTH DISPARITIES: WHAT HAVE WE LEARNED FROM TWO 40 YEAR COHORT STUDIES IN SCOTLAND?

INTRODUCTION:  A better understanding of what influences the human lifespan requires mortality data collected from well-described representative population samples over many years. We summarise the main findings of 43 peer-reviewed papers published in 1978-2013 that analysed mortality rates in two cohorts followed-up for about 40 years.

METHODS:   In 1970-73, the Collaborative study recruited 6022 males and 1006 females of working age from 27 workplaces in Central Scotland. In 1972-76, the Renfrew and Paisley study recruited 7049 males and 8353 females aged 45-64 from the general population of two Scottish towns.  On recruitment, participants underwent an extensive questionnaire, biological measurements and blood sampling. Their data were linked to the Scottish death register and all deaths recorded, permitting a wide range of analyses of mortality rates. A sub-sample of 938 was linked to the results of a validated mental ability test conducted on all 11 year olds in Scotland in 1932.

RESULTS:   Lower occupational class of father and self, lower educational attainment and more disadvantaged area of residence all made independent contributions to higher mortality. Socially mobile participants had intermediate mortality rates. Mental ability at age 11 was inversely correlated with mortality before age 65 but not after. Smoking had a bigger adverse effect on mortality than any other factor studied. Heavy drinkers had high mortality rates, especially when combined with smoking or obesity. Poorer lung function and higher blood pressure at recruitment were strongly associated with higher mortality but plasma cholesterol and mental stress levels were not.

CONCLUSIONS:   These cohorts show the cumulative adverse influence of many factors over the lifecourse, among which smoking, other causes of lung and cardiovascular damage, and heavy drinking were prominent. The most disadvantaged fared worst. Achieving more equitable social and environmental conditions and discouraging damaging behaviours may reduce such disparities in future generations.