Which older adults were examined in BASE?
How were they followed up?
First Occasion of Measurement (T1): 1990–93
Cross-Sectional Assessment Phase
An initial sample of 2,297 old persons living in former West-Berlin (aged 70 to over 100) was drawn from the obligatory city register for use in the field. 83% of these addresses could be verified, resulting in a verified parent sample of 1,908 old persons who were asked to take part in the study. Of these, 22% refused outright to take part. A further 12% could not take part for health or ethical reasons, whereas 66% were prepared to provide some basic information on the level of a multidisciplinary Short Initial Assessment, 49% (N = 928) took part in the Intake Assessment, and 27% (N = 516) continued and completed the entire 14-session Intensive Protocol.
As to be seen in the figure, the core sample of people taking part in the Intensive Protocol was stratified by age and gender with 43 men and 43 women in each of the six age groups (70–74, 75–79, 80–84, 85–89, 90–94, and 95+ years; total N = 516). This allowed comparison of subgroups (e.g., among the very old or those affected by dementia) with sufficient statistical power. The figure also shows the age distribution of the older adults registered in 1990 in West-Berlin. Note the unequal distribution of older men and women.
In-depth selectivity analyses comparing the persons on different participation levels showed that the Intensive Protocol sample remained representative of the parent population despite some small positive selection effects (all below half of a standard deviation). In particular, there was no indication that correlation patterns and variances differed among the participation levels. See also Selectivity.
Only the 516 Intensive Protocol participants were followed in examinations over the subsequent years (if they had agreed to be re-contacted). In addition, mortality data on the parent sample are regularly provided by the city registry
Second Occasion of Measurement (T2): 1993/94
431 of the 516 Intensive Protocol participants were still alive at the time of the first follow-up. 84% (N = 361) of these completed the protocol consisting of the single-session multidisciplinary Intake Assessment.
Third Occasion of Measurement (T3): 1995/96
At T3, 313 participants had survived. 78% (N = 244) took part in a repeat of the Intake Assessment, and 66% (N = 206) completed the reduced Intensive Protocol consisting of six sessions.
Fourth Occasion of Measurement (T4): 1997/98
At T4, 239 of the 516 participants in the Intensive Protocol at baseline were still alive. 69% (N = 164) participated in the Intake Assessment, and 55% (N = 132) completed the entire reduced Intensive Protocol.
Fifth Occasion of Measurement (T5): 2000
At T5, 164 persons were still alive. 88 completed the Intake Asssessment enriched by Psychiatry measures. 82 took part in the Intensive Protocol which was reduced to two Psychology sessions and a dental examination.
Sixth Occasion of Measurement (T6): 2004
At T6, 104 persons had survived. 47 completed the Intake Assessment enriched by Psychiatry measures and 46 finished the Intensive Protocol, which again consisted of two Psychology sessions and a dental examination.
Seventh Occasion of Measurement (T7): 2005/06
At T7, 93 were still alive, and 38 completed the Intake Assessment enriched by Psychiatry measures; 37 underwent a burst of six Psychology sessions within two weeks.
Eighth Occasion of Measurement (T8): 2008/09
At T8, 62 had survived. 23 participants were assessed in the Intake Assessment enriched by Psychiatry measures and 22 completed the Intensive Protocol consisting of two Psychology sessions and two medical sessions. 19 of these also took part in two dental assessments.
Delius, J. A. M., Düzel, S., Gerstorf, D., & Lindenberger, U. (2015). Berlin Aging Studies (BASE and BASE-II). In N. A. Pachana (Ed.), Encyclopedia of geropsychology. Springer. https://doi.org/10.1007/978-981-287-080-3_44-1
Nuthmann, R., & Wahl, H.-W. (2007). Technical report for the first wave of the Berlin Aging Study: Field procedures and sample recruitment strategy (1990–1993) (Materialien aus der Bildungsforschung Nr. 82). Berlin: Max Planck Institute for Human Development. Full text
See also Publications