sampling and until emigration, death, or end of study pe- riod (January 1, 2001), whichever event came first. Infor- mation on emigration and death was retrieved from the Danish Central Population Register, which is continuously updated. We used the Kaplan-Meier method, and the influ- ence of ACE genotype on survival was ascertained using the log-rank test. Subsequently, a Cox proportional-hazards regression analysis was undertaken to determine ACE gen- otype as an independent risk factor controlling for the ef- fects of sex, age, cognitive function (MMSE score), and self-rated health. These parameters were included in the analysis because they were associated with ACE genotype and survival. Education, which also differed by ACE geno- type, was omitted from the final model, as it did not contrib- ute significantly in explaining survival. The proportionality assumption was confirmed with a log minus log survival function plot.

Physical Abilities

Self-reported data about physical abilities were obtained from 683 individuals. The median strength scores from the two surveys as well as their mean relative difference did not vary substantially by ACE genotype (Table 2). The com- posite endurance score of self-reported walking, running, and cycling from the 1999 survey did not differ by ACE genotype (Table 2). The maximum handgrip pressure was measured in 488 individuals with a mean-grip strength (SD) of 24.4 kg (8.6). Grip strength was highly dependent on sex, age, height and weight, but since height and weight were comparable in the three ACE genotypes (Table 1) this measure was analyzed age-adjusted and sex-stratified as other physical performance measures. Mean grip strength did not vary by ACE genotype (Table 2). The chair stand test was successfully completed by 426 individuals. The mean time (SD) used was 12.5 seconds (4.5) and the mean increase in pulse after five chair stands was 7.8 (4.8) heart- beats per minute. Both the time used to complete the test and the increase in pulse were highly comparable in the ACE genotypes (Table 2). The proportion of twins unable to perform the grip-strength and chair stand test did not vary by genotype (results not shown).

The physical and cognitive functioning and survival among individuals from intact dizygotic (DZ) twin pairs that were discordant for ACE genotype were finally com- pared using the Sign test.

Study Population

The population comprised 684 individuals (Fig. 1), 450 (65.8 percent) females and 234 (34.2 percent) males. The mean

TABLE 1. Baseline characteristics of 684 twins participating in the longitudinal study of aging danish twins (LSADT) 1997 survey

Females Males ACE Genotypes II ID DD II ID DD N (percent) 101 (59.8) 231 (67.2) 118 (69.0) 68 (40.2) 113 (32.8) 53 (31.0) Age, mean  SD 78.5 I+ 4.6 78.5 te 4.6 77.0 Je 4.6 76.8   3.3 78.4 + 4.3 77.9 ye 3.9 BMI, mean   SD 24.5 I+ 4.1 23.5 I+ 3.8 23.4 f+ 4.1 26.0   3.3 25.2 1 +1 2.8 24.8   3.3 Education, ,> 8 yrsa 14 (13.9) 44 (19.2) 28 (23.9) 9 (13.4) 19 (17.0) 18 (34.0) Smokers, ever 57 (56.4) 121 (52.4) 56 (47.9) 56 (83.6) 91 (81.3) 42 (80.8) Alcohol, ,>] 10 units/week 8 (8.7) 29 (13.6) 16 (15.0) 24 (40.0) 39 (37.9) 18 (38.3) b Self-reported diseases Diabetes 6 (5.9) 10 (4.3) 5 (4.2) 2 (2.9) 11 (9.7) 6 (11.3) Hypertension 33 (32.7) 66 (28.6) 33 (28.0) 11 (16.2) 26 (23.2) 14 (26.4) c Other cardiovascular 13 (12.9) 31 (13.4) 17 (14.4) 10 (14.7) 22 (19.5) 7 (13.2) Stroke 3 (3.0) 12 (5.2) 5 (4.2) 7 (10.3) 5 (4.4) 6 (11.3) d Respiratory 9 (8.9) 27 (11.7) 12 (10.2) 17 (25.0) 17 (15.0) 14 (26.4) Poor/very poor self-rated healthe 7 (7.1) 17 (7.5) 11 (9.3) 3 (4.8) 3 (2.8) 6 (11.3)

No statistically significant differences among genotypes if not otherwise stated. Differences were tested with Logistic regression for categorical data and with multivariate linear regression for continuous data with the DD genotype as reference, controlling for age of the participants. Twins from intact pairs were analyzed as clusters of two in the multivariate models. aMales, DI: p  0.02, II: p  0.02 bParticipants were asked if a physician had ever told them that they suffered from any of the mentioned diseases. cAngina, myocardial infarction or heart failure dChronic bronchitis or asthma

Cognitive Abilities

surveys were comparable in the three ACE genotypes (Ta- ble 3). Although not statistically significant the proportion of individuals with a score below 24 was approximately seven percent higher in participants with the II genotype of

The MMSE-test was completed by 674 persons with a me- dian score of 27.0 (quartiles 24.0–28.0). The median test scores and the mean difference in scores between the two

TABLE 2. Physical abilities and ACE genotype

Females Males ACE genotype II ID DD II ID DD Self reported physical abilities in 1997 Median strength score (quartiles) 3.4 (2.5, 3.7) 3.5 (2.6, 3.7) 3.3 (2.5, 3.7) 3.5 (2.5, 3.7) 3.5 (3.2, 3.8) 3.5 (2.9, 3.7) N 101 231 117 68 113 53 Self reported physical abilities in 1999a Median strength score (quartiles) 3.3 (2.5, 3.6) 3.4 (2.7, 3.5) 3.4 (2.5, 3.5) 3.5 (2.7, 3.6) 3.4 (2.6, 3.6) 3.5 (2.7, 3.7) Mean endurance score (SD)b 4.7 (1.1) 4.7 (1.1) 4.8 (1.0) 4.2 (1.2) 4.4 (1.2) 4.4 (1.4) N 73 173 89 54 91 42 Relative difference in self reported abilities 1997 to 1999 Mean relative strength score difference (SD) 0.05 (0.2) 0.05 (0.2) 0.02 (0.2) 0.07 (0.2) 0.07 (0.2) 0.05 (0.2) Measured physical performance in 1999 Mean grip strength (SD), kg 20.1 (4.6) 19.6 (4.7) 19.5 (5.0) 34.2 (7.2) 32.3 (6.9) 31.7 (8.8) N 65 161 86 51 85 40 Mean time to complete five chair stands (SD), 12.1 (4.2) 12.9 (4.8) 12.9 (5.5) 12.4 (3.7) 11.7 (3.3) 12.4 (5.1) seconds Pulse increase after five chair stands (SD), bpmc 7.4 (4.6) 7.4 (4.4) 7.7 (4.7) 8.5 (4.6) 8.9 (5.9) 7.9 (4.7) N 60 146 75 39 73 33