Anthropometry in the elderly. Population studies on longitudinal changes, secular trends and risk for morbidity and mortality

Sammanfattning: The aims of this thesis were to a) describe longitudinal changes in height and body weight (BW) between the ages 70 and 95y; b) describe secular trends in height and BW of 70-year-olds and their relation to social and lifestyle factors; c) investigate waist circumference (WC) and body mass index (BMI) at age 70 as risk for stroke during a 15-y follow-up; and, d) examine the relationship between 1) BMI at age 70 and 15-y all- cause mortality, 2) the percentage of weight change from age 70 to 75 and subsequent 5- and 10-y mortality. The studies were performed within the framework of the gerontological and geriatric population studies in Göteborg, Sweden-the H70 studies. In the H70 studies, 3,128 70-year-olds (1,426 males and 1,702 females) from four cohorts participated in medical examinations during 1971/72 (Cohort I; 449 men and 524 women), 1976/77 (Cohort II; 474 men and 562 women), 1981/82 (Cohort III; 302 men and 317 women), and 1992 (Cohort V; 201 men and 299 women). Longitudinal changes in anthropometry were studied in Cohort-I where participants and survivors were followed from ages 70 to 95 with 11 examinations in between. Secular trends were studied in participants of all four cohorts (I, II, III and V). Morbidity (stroke) and mortality were studied in participants (2,628) of three cohorts (I, II and III). BW and standing height were measured in the morning and were recorded to the nearest 0.1kg and centimeter with the subjects wearing light clothes. BMI was calculated from weight (kg) divided by height (m) squared. WC was measured horizontally half-way between the lowest floating ribs and iliac crests with subjects in standing position. From ages 70 to 95, height decreased 4 and 5 cm and BW decreased 3 and 5 kg in males and females, respectively. Due to the decrease in both height and BW, BMI was less affected. Individuals of later-born cohorts were found 1 to 2 cm taller and 1.5 to 6.3 kg heavier than earlier-born cohorts. "Year of birth" was a positive predictor for BW (p<0.001) and BMI (p<0.001) in males, and for height (p<0.05) and BW (p<0.01) in females. Physical inactivity was a positive (p<0.01) and "current smoking" a negative (p<0.001) predictor for BMI in both sexes. "More than basic education" was a positive predictor for height (p<0.001) in both sexes and a negative predictor for body weight (p<0.01) and BMI (p<0.001) in females only. During the 15-y follow-up from age 70, the adjusted relative risk (RR) for non-fatal and all strokes in males were 1.69 (95% CI 1.03 - 2.78) and 1.62 (95% CI 1.06 - 2.47), respectively, in the highest WC quartile compared to the lowest quartile. In females, an elevated RR in the highest WC quartile 1.49 (95% CI 1.02 - 2.25) for all strokes disappeared after adjustment for systolic blood pressure. In males, the adjusted RR in the highest BMI quartile for non-fatal stroke and all strokes were 1.72 (95% CI 1.07 - 2.77) and 1.66 (95% CI 1.10 - 2.51), respectively. In females, RR for any stroke across the BMI quartiles was not found to be significantly different. In both sexes, neither WC nor BMI were risks for fatal stroke. The RR for 15-y mortality from age 70 were highest in the lowest BMI quintiles of males 1.20 (95% CI 0.96 - 1.51) and females 1.49 (95% CI 1.14 - 1.96). After exclusion of first five-years death, no excess risk were found in males for following 5- and 10-y mortality across the quintiles. However, a U-shaped relation was observed in females after such exclusions. A weight loss of ³10% between ages 70 and 75 meant a significantly higher risk for subsequent 5- and 10-y mortality in both sexes.The results indicate that height and BW decreases significantly after age 70 and more prominently in females. Trends in increasing height and BW among the new generations of 70-year-olds are partly attributable to variations in social and lifestyle factors. Both high BMI and WC are risks for stroke in elderly males. On the other hand, both low BMI and weight loss are risk for mortality in both sexes. The results might be of importance to the understanding of anthropometry and its relation to morbidity and mortality in the ageing population.