The mean age of the participants was 73.0 (SD 6.4, range 64.0‒97.0) years and 57% were women. More detailed baseline characteristics of 1106 study participants are shown in Table 1.
Three percent of participants were characterized as frail according to FS, 25% according to FI and 18% according to PRISMA-7. Figure 1 shows a Venn diagram of overlapping participants categorized as frail by FS, FI and PRISMA-7. All of the participants categorized as frail by FS were also categorized frail by FI. Frailty (both pre-frailty and frailty) was more common in women than in men according to FI and FS, but according to PRISMA-7, more men were frail than women.
Only 8% (9% of women and 7% of men) of the participants were self-reportedly unable to walk 400 m.
Altogether 14% (n = 159) of participants rated their health as poor. The proportions of men and women in different groups of SRH (good, intermediate and poor) were similar: 40, 46 and 15% for men, and 41, 45 and 14% for women, respectively.
Of the participants, 212 (31.1%) women and 130 (26.5%) men were alive at the end of 2016.
Of the participants self-reportedly able to walk 400 m at baseline, 65% were still living at home, 12% institutionalized and 23% deceased after 10 years (at the end of 2008). After 18 years (at the end of 2016) the proportions were 28, 28 and 44%, respectively. Of the participants self-reportedly unable to walk 400 m, 10% were living at home, 43% institutionalized and 47% deceased after 10 years. After 18 years the proportions were 0, 47 and 53%, respectively.
Of the participants with good SRH at baseline, 72% were still living at home, 12% institutionalized and 16% deceased after 10 years. After 18 years, the proportions were 32, 29 and 39%, respectively. Of the participants with poor SRH, 29% were living at home, 26% institutionalized and 45% deceased after 10 years. After 18 years, the proportions were 6, 40 and 53%, respectively.
Prevalence of institutionalization
When analyzing the proportion of participants institutionalized in the municipality of Lieto, we included participants who had been institutionalized before baseline. We only took into account the participants deceased by the end of 2016, to count the proportion of participants institutionalized during their lifetime. This left us with 831 participants, of which 339 were institutionalized (40.8%). There was a higher prevalence of institutionalization in women (48.9%) than in men (30.2%).
The mean age of the participants at the time of institutionalization and the mean time spent living in an institution are shown in Table 2.
Cox models for frailty and institutionalization
During the 10-year follow-up, both being frail and pre-frail according to FS and FI were associated with a higher risk of institutionalization in unadjusted Cox regression models (Table 3). After age- and gender-adjusted (items of PRISMA-7) analyses for FS and FI, the associations persisted for FI; pre-frailty according to FS also remained significantly related to higher risk of institutionalization. Also using the binary (robust or frail) PRISMA-7, being frail was associated with a higher risk of institutionalization during the 10-year follow-up.
During the 18-year follow-up, being pre-frail according to FS and both being pre-frail and frail according to FI were associated with a higher risk of institutionalization in unadjusted models (Table 4). After adjustments for age and gender, only being frail according to FI significantly associated with a higher risk of institutionalization. Also being frail according to PRISMA-7, was significantly related to a higher risk of institutionalization. Figure 2 shows the rates of institutionalization by FI, FS and PRISMA-7 during the 18-year follow-up.
The association of frailty and institutionalization did not significantly differ between men and women either in 10- or 18-year follow-up by FI or PRISMA-7; using FS, being pre-frail predicted a significantly higher risk of institutionalization in women (1.85 [1.41–2.43], p < 0.001), but not in men (0.98 [0.63‒1.53], p = 0.930) during the 18-year follow-up.
Cox models for walking ability, self-rated health and institutionalization
In an unadjusted model, the self-reported inability to walk 400 m and poor SRH were associated with a higher risk of institutionalization during both follow-ups. After adjustments, the associations persisted in 10-year follow-up. Figure 3 shows rates of institutionalization by self-reported walking ability and SRH during the 18-year follow-up.
No significant interaction was found between gender and self-reported walking ability in predicting the risk of institutionalization during either follow-ups. Poor SRH, instead, predicted a higher risk of institutionalization in women (1.85 [1.27‒2.68], p = 0.001) but not in men (1.49 [0.86‒2.60], p = 0.157) during the 18-year follow-up.