Twenty-year dynamics of serum cholesterol levels in the middle-aged population of eastern Finland.

BACKGROUND

In cross-sectional analyses, serum cholesterol levels differ among different age groups. However, secular time trends in cholesterol levels can be seen across age groups in a population. A birth cohort analysis provides useful information on the combined effect of age and time on changes in serum cholesterol levels.

OBJECTIVE

To analyze the 20-year dynamics of serum total cholesterol levels in relation to age, sex, birth cohort, time period, mortality rate, and changes in the intake of saturated fats.

DESIGN

Cross-sectional measurements of serum total cholesterol levels in five independent population surveys done in 1972, 1977, 1982, 1987, and 1992.

SETTING

Kuopio and North Karelia provinces in eastern Finland.

PATIENTS

Random sample of 16,711 men and 17,542 women 25 to 64 years of age. Persons in the oldest birth cohort were born in 1913; persons in the youngest birth cohort were born in 1967.

MEASUREMENTS

Total serum cholesterol levels and daily intake of dietary fat.

RESULTS

Between 1972 and 1992, mean cholesterol levels decreased with time in each age group and for both sexes. According to the cross-sectional data, cholesterol levels increased with age and increased more steeply in women than in men. Contrary to these data, cholesterol levels in birth cohorts did not increase with age. Cholesterol levels did not change at all within birth cohorts of women and started to decrease after 45 years of age in birth cohorts of men. Cholesterol levels in the youngest birth cohorts (persons 25 to 29 years of age) entering the study each study year were markedly lower than levels in the same age group in the previous survey of risk factors. Daily intake of saturated fat decreased markedly between 1972 and 1992. Most of this decrease could be explained by change in intake of liquid dairy products and spreadable fats. In both sexes, changes in saturated fat intake were correlated with the time period, whereas the association with age was weak.

CONCLUSIONS

In this Finnish population, total serum cholesterol levels are more closely associated with birth cohort than with age. Changes in dietary intake of saturated fat over time may account for changes in cholesterol levels. This finding suggests that community-based strategies for preventing cardiovascular disease can affect most of the population.